Is there any evidence that "companies, figures, games, movies, etc" have stopped using Twitter to promote their products and/or use Twitter as a support channel? And doubly so that they did this because of their own political views?

I find it really hard to imagine that there is a significant number of such companies that is just waiting for Milo Yiannopoulos, Steve Bannon, and Alex Jones to be unbanned, so they can finally resume using Twitter for their commercial purposes.