What could help Mastodon grow significantly is if the moderation on a large number of instances was toned down a bit. What happened to Wil Wheaton was a bit nuts. And conservative opinions are often banned due to being agressively labelled as hate or racist when they are usually not technically so. Most people don't want to be part of a social justice warrior authoritarian "fall in line or we will ban you" community.
Sure, people could set up their own instance. Federation is awesome. But if almost all other instances don't talk to them, they have to build a community from scratch, and it's usually not worth it.
Sure, people could set up their own instance. Federation is awesome. But if almost all other instances don't talk to them, they have to build a community from scratch, and it's usually not worth it.