This is sort of a divergent opinion I'm aware but I think Lovecraft's extremely weird way of writing came from the fact that he was a complete nervous wreck. Like we all know he's RAYCISS but dude was literally afraid of fucking everything. Everything. Read his more obscure works some time, they detail his fears of not just foreign people but foreign religions, cultures, practices, even other white people (he was inspired to write Shadow Over Innsmouth because he discovered he had a Welsh ancestor. The horror.) and also things like bugs, rats, poor living conditions in general, mental illness, the idea of past civilizations, the idea of aliens, the idea of other planets, the idea that there might be invisible things we cannot see, and literally things as basic as the size of the fucking universe. Literally afraid of everything.
Christ if I had that level of anxiety I'd never leave my fucking house either.
I wouldn't be surprised if he never actually was a writer at all and his collected works are just something some therapist wrote down after listening to the man talk.