Last week I created a brand new Facebook account as I recently moved to a new city and am somewhat desperate to meet people, and Facebook events can be useful for this (as much as I loathe Facebook, my mental health is a bit more important right now). I got banned after about 2 minutes. I didn't actually do anything on the platform. I managed to click to about 2 or 3 pages.
What set this off? Who knows. Maybe some browser settings? Previous user(s) of my IP address? Those pages I clicked on? Something else? It surely wasn't anything I actually did as I didn't really interact with the platform at all.
I suspect that if I asked some high-up Facebook engineer to look in to it they wouldn't be able to actually give me an answer either beyond "The Algorithm determined there were risk factors".
As to your FB ban, I'm sorry that happened but I have no insight to share.
Instagram has always banned my accounts for suspicious behaviour on whatever page is first used after the account is created - the only way they offer to progress is to give them a phone number. It's a pretty transparent grab for more info to sell.
Funny enough, when I checked after posting my previous comment I could log in and it was all good. I didn't do anything, and now I got an email saying "Your Facebook account has been disabled. This is because your account, or activity on it, doesn't follow our Community Standards". All I did was log in, view the home page, and close the tab.
I requested another review :-/
For every account banned, one million new users will enter the Google ecosystem. Bans cost them nothing in the long run, but having reviews to justify bans would.