This is a bit of a silly response on your part. You're not answering the question of WHY people are on FB and not on the little sites like existed 20 years ago before FB. It's called the network effect. You have friends, your friends have friend, those friends have friends. Rather than there being 30 bajillion separate sites representing these friends connections, people go "hey, why not one site with everyone there".
Said little sites may run for a bit and die, and the massive monolith remains, at least until another monolith replaces them.
I'm not sure how that applies here? The argument is that a p2p network will be flooded with bots?
There's a p2p network I use today which doesn't have that problem, probably due to its small size. Meanwhile all the big platforms do — including this one!
Early Facebook was kind of a great mix. It had enough people on it, it was making money, and the advertising was much more reasonable. At the time it really was a place to connect with IRL friends.
(If we hit the stretch goal, we can upgrade to a raspberry pi!)