if I look at the viewcount on bitchute the most popular channels are in the thousands when it comes to views. Not sure what Gab's or Rumble's numbers are, but I am almost certain they're significantly diminished, including in ad revenue for creators compared to giving them mainstream access.

And that is enough. People argue against deplatforming as if the point is to somehow cure or enlighten the people who get kicked off.

The actual point is to destroy the material means they require to operate. If you can diminish their audiences and revenues it will impact their reach and that means their influence and the financial incentive to keep going decreases.

There's no evidence they're 'thriving' in the underground, and as long as they marinate in the underground that is good enough.