I know next to nothing about this topic but heard in an interview with Ventura, that Hogan was the only one of that league (or how they call it) who had already signed a fat contract with a higher league and that the unionization would have put that into risk of not proceeding.

Edit: Found the interview. It was a bit different than I remembered but not much.

https://youtu.be/nt5mRyIyOzU?t=2947 (at 49:07)