If you really want to learn more, I'd suggest reading one of ST Joshi's biographies about Lovecraft.

I Am Providence is the biography by which all others are judged. Some people find it a bit too detailed and/or dry but I'm not sure what some expect.

Lord of a Visible World is a curated selection of letters by Lovecraft, effectively an autobiography.

Nightmare Countries is a bit lighter weight than I Am Providence, some find it more palatable.

Additionally you may be interested in the Voluminous podcast by the HP Lovecraft Historical Society. They go in depth on select letters.

More to the point, you are not going to get good answers from youtube, twitter, reddit, etc on Lovecraft. The video you mention in particular is one example of a poorly researched essay that seems to pull more from popular (not necessarily factual) talking points on social media.

Lovecraft was inspired by many things and writers. Specifically when it comes to his monsters such as Cthulhu, the Deep Ones, Dagon, etc, you might say that his distaste for seafood had some influence. Some people will take that statement and hyperbolize it into 'Lovecraft wrote about things he was terrified of and he was terrified of fish!', that's nonsense, he simply didn't like eating it. Lovecraft was an avid enjoyer of aquariums. Unfortunately that blog's suffered from a couple migrations and the images are gone but the gist is there.

Bottom line though is if there's something you want to know about Lovecraft, you need to read a biography (and select ones at that).