I don't think I've read most of it. I am just investigating. My fb page of 15+ years was hacked and stolen and I am not sure through where and how that happened. And currently my identity/brand is being used to post explicit video content on the page daily :/
Discussion
Without knowing more, it sounds like an OPSEC issue. When was the last time you changed your Facebook password? Did you use the same password elsewhere? It could be on the dark web, associated with the same email. A credential stuffing attack seems likely.
Well, I was getting messages from fb that they will soon lock me out unless I go through their process to better protect my account.
I didn't take action on time. Got locked out. Messed a bunch trying to login again. Eventually created double authentication. And then one or two week later this content started getting posted on my page and I no longer was an admin. :/