New social networks are best modeled as new countries. 

Who has the most incentive to emigrate from the old to the new?

those with nothing to lose and everything to gain

one of the reasons why most early fc users with large audiences on the bird app churned, but those with no/low audience remained and stayed active

I’m still here, despite I have 20k+ followers on Tw… ehm, X. The reason? In my case it’s just being an early adopter. I like being an early adopter, it usually something that brings value in the long term.