I'd love to see similar plots after you remove the primary servers in each! To give you a rough idea: 78% of the people I follow on Mastodon are not on the primary instance, and over 80% of my followers are not either.

> Anecdotally, Bluesky feels more lively for me because that seem to be the default destination for Twitter refugees.

It likely is the default of Twitter refugees, but as a Mastodon user none of this is relevant to me! I don't care how many more users a network has, as long as the one I'm on has a healthy number. Very few of the people I follow are likely to leave Mastodon.