All of them are still bigger than Mastodon. After 6 years, Mastodon failed to show itself to be a proper alternative even during the so-called 'exodus' from Twitter. Given that it is smaller than those social networks, I regard that as a catastrophic failure.

6 years is not early days and Mastodon failed has still failed to attract users from Twitter 2 months ago. No chance of a significant amount of serious users from other social networks migrating over.

Mastadon wasn't built for conservatives though. Truth and it's ilk are built specifically because of conservatives feeling censored. They have a reason to go there. Mastadon has nothing.