No, I think the real major reasons are marketing related. For example, Facebook's network effect is very strong, even compared to sites like Twitter and Instagram. The service is only replaceable by one that grows extremely quickly, to the point things don't settle down enough for the site to feel like a ghost town.
And it ties into the real reason said effect is so strong.
These P2P and decentralised networks are only appealing to a certain minority of users.
They're basically marketed as 'censorship resistant' or 'free speech focuses'. And while these are nice things to be, they're not a selling point for 90% of the social media userbase. The vast majority of people either don't feel they're being censored or don't really care about anything controversial.
As a result, the only people using these services are niche groups using subject specific networks and activists banned or unwelcome from the major ones. It's like why Voat failed to unseat Reddit; because the only people who joined were those interested in discussing controversial issues and hence the site wasn't useful for people wanting to discuss more mundane things.
It's the social and marketing factors that really sunk any P2P attempts at a Facebook clone (or any other decentralised social networks). They just don't have value for people wanting to discuss non controversial things.