So I've been a huge fan of horror since as long as I can remember. As a kid, I read HP Lovecraft and Stephen King (and all the classic horror stories as well) and watched tons of ghost, vampire, zombie, demon, and so on horror flicks, and back in college I would typically watch around 10 horror movies every week, so I have never had trouble suspending disbelief. HOWEVER, it's always a problem when a show or movie tries to explain itself and doesn't have what is needed to convince the viewer of the explanation. Then, instead of just accepting "okay, this is how ghosts work," you start going "wait, that doesn't make sense. Why? How? Huh?"
Like, Bly Manor has an entire episode (by far, the slowest, least scary, and most boring episode of the whole season) dedicated to what happened to Viola that started everything. But it's... nothing. A priest asked her to repeat some words and she said "no" (which the show interpreted her as saying "no" to God, though it never shows her as being a witch or some evil human being), then after surviving 6-15x longer than the doctor said she would, her sister suffocates her (and you can kind of see where the sister is coming from after how condescending, harassing, and abusive Viola is), and even though she never killed anyone when she was alive, she ends up just illogically massacring random people as a ghost (her first two victims being a random doctor and a random vicar). Um... okay? So how did she get this power? They say she just had a strong desire to remain and that that desire to remain made every other character who died on the property remain as a ghost too. Well, simply desiring not to die or to stay in the land of the living isn't remotely rare, so what was the reason? Her sister killing her or her sister "stealing" her clothing years and years after she died, even by typical horror movie/show standards, seems like a pretty shitty reason to haunt a place and kill anyone who just happens to be standing in front of you when you're walking somewhere. We've already established from her past that she isn't some horrific serial killer or legendary demon worshipper. After she kills her sister for opening the chest with her clothes, her husband understandably throws that chest in the water for believing it to be cursed. I mean, well, yeah, if you found your wife looking like something out of The Ring, dead and 60 years older than she actually was, just outside of your dead wife's chest that she was forbidden from opening, who could blame you for thinking it's cursed and dumping it? (and who's to say it wasn't cursed? I mean, it basically was, right?)
So, she dies and is 100% the same as alive, but just transparent and insanely super powered. But for some reason her memories (and face? what?) fade as time goes by? Okay... how? why? I mean, normally your memories are stored in your brain, and she doesn't have one of those anymore, so what are they disappearing from? If it's some cheesy thing of "your memories disappearing because people who remember you die," then why does she still have some memories of 350 years ago when no one who could remember any of that is still around anymore? And don't tell me not to try to figure out how ghosts work. If they hadn't brought up these things, I wouldn't have asked questions about them (just like I didn't ask questions about the ghosts in Hill House).
How did she go from a grumpy sick person to some supreme being who can instant-kill anyone who gets in her way, no matter how innocent they are? Why is she the only ghost with any powers? And why are the other ghosts scared of her? She doesn't look remotely scary and the only ghosts who ever try to stop her only have momentary discomfort but then are just the same as always. I mean, they're already dead and the show never introduces the possibility of Viola annihilating ghosts from existence. Anyone who's alive gets killed in a single touch or a few second choke (except when it isn't convenient for the story, such as with Dani)? Why can no humans and no ghosts stop her or slow her down? Why do none of the ghosts even try to stop her until the final episode? What is so special about this Viola character? Episode 8 shows her as a pretty bland and boring socialite from the late 1600s. If grumpiness is enough to make you an all-powerful multi-generational ghost, then why is she the only one there like that? When Viola is about to drown Flora, the ONLY ghost that tries to stop her is Hannah, who can't do anything for no reason explained. The only human that tries to stop her is Uncle Henry, who dies instantly when Viola touches him (yet he comes back to life as soon as Dani "invites" Viola into her - no explanation given there either). And how the hell does Viola saying the same thing that Flora had said to Rebecca to Viola (who supposedly can't remember who she is, what her name is, who her daughter is, etc. etc.) count as "inviting" her into her body? If Viola has such a strong will that it kept her at Bly as an insanely powerful ghost for over 350 years, then why can't she control Dani when Peter Quint had total control over Miles and Rebecca had total control over Flora? And one could argue that Miles and Flora had more assertive personalities than Dani did. In most horror movies, when they bother to go to the trouble of showing who some terrifying ghost was before they died, they usually try to make you terrified of that person as a human so they're even more terrifying as a ghost, but Viola is just bland and boring as a person, and isn't particularly interesting as a ghost either, yet somehow has insane powers. Well... She can't teleport or float or... I guess she just has "super strength" and "immortality" and that's it. But no reason is ever given. She's also not usually very scary. She has maybe one or two jump scares in the whole show, but most of the attempts at jump scares (such as her being reflected off the plate Dani's washing in the last episode) aren't remotely scary, and you wonder why Dani would even drop the plate after so many years of seeing reflections of Viola.
And moving away from her, why are most of the ghosts on the property both physically and visually able to interact with the living to the point that none of the living ever realize that they're ghosts? That's not typical at all in horror novels, short stories, movies, TV shows, or video games, and in the rare cases where it does appear, they usually have some explanation for why that's the case, since it's so outside the norm for ghost stories. Here, though, it's never explained. Hannah, I assumed from Episode 1, was dead because she never ate anything, but then again, there's an entire episode where she does nothing but drink wine. So she can't eat, but she can drink? The whole thing with Peter and Rebecca being able to possess people also isn't explained. And even more so how he "permanently" possesses Miles (which Rebecca says can't be undone, yet Dani undoes it somehow by "inviting" Viola into herself, yeeeeeah, that bullshit made zero sense too), yet somehow this can let him get off the territory. Okay, when it comes to specifically not being able to leave the territory, that itself is not too uncommon. A lot of versions of poltergeists are unable to leave a certain location (although there are also a lot of versions of poltergeists that CAN leave that location, but they just like it there since maybe that's where they died or whatever, so even if they leave it, they always come back).
And then they had the uncle's "split personality" / "evil version of himself," which only appeared in ONE of the episodes, and it was pretty clear that the people who made the show were like "Uh, well, he's not dead, so we can't do the whole ghost thing we do with a lot of the other characters." "HEY, LET'S GIVE HIM AN EVIL IMAGINARY SPLIT PERSONALITY... THAT WE NEVER ADDRESS BEFORE OR AFTER THAT EPISODE!!!"
Dani's fiancé's ghost worked because they never explained it. They never had him chat with her. They never had him massacring tons of innocent people one second and behaving like a normal human being who just happened to be a ghost the next. In fact, it's one of the rare places in the show where they kind of follow the original novel's idea that she might be insane. Then again, he didn't disappear when she burned his glasses, but he just never appeared in any episodes after that, so it would've just made more sense if they had him vanish at the end of the episode instead of just having the sparks shoot up and him just keep standing there as the episode ended with no explanation of WHY he was just gone after that. I didn't want a lengthy explanation. They could've just had him slowly walk away or just fade away so we could interpret it as "She burned his glasses and made it clear that she doesn't want to see him anymore, so he disappeared" and left it at that.
I could go on and on about this, but this really boils down to my biggest problems with this show.
In short, NOTHING about the ghosts in Bly Manor make ANY sense. I never had any questions like this with Hill House. And maybe that's because they didn't do things that made me ask these kinds of questions. But that's specifically what makes this very poorly done. This is how NOT to make a ghost TV show/movie.