Say I have 100 followers and each of them have 100 followers.

Then say I make a post and all of my followers repost it.

That’s an explosion of updates that need to be sent around for 101 interactions.

These major social media platforms handle millions of interactions per second with accounts that have millions of followers and posts that get hundreds of thousands of reposts.

When there’s a centralized system, it’s easier to make sure everyone gets all their posts. Very little need to propagate every single update across every node in your whole network. From a user standpoint it’s seamless as well

It’s nothing unsolvable, but it’s much harder than a centralized social media platform while providing no visible benefit for the average, non technical, user.