You've been following MMA long enough you should understand the point here. MMA prospects are getting paid peanuts and furthermore, not allowed their own sponsorship, not to mention all the other stupid crap like fight kits. The Conors and Brawks are not going to last forever and developing talent could start in another org like GB and do better financially on their way up, building themselves and that org. Think about all the things 99% of the fighters complain about being wrong with UFCs pay, ranking, and title systems and you can easily see the time is good for a startup like this.
One would have to be pretty dense to think a promotion is going to start by paying the very top guys when they could grab 20x as many top 10 yet lower paid fighters and build the org there. Also, obviously, why would a person think they are starting by building full cards when they could simply start adding a few MMA fights to boxing card. The ring/cage swapout really wouldn't be such a big deal in a venue that was setup right for it.