The Fertittas and Dana probably have a no-compete clause that lasts something like 5 years. They would need to use $100-$200 million to establish a rival to the UFC that could kick its ass. They could offer Conor and a few top stars a chance to buy in. They wouldn't need nearly as large of a fighter pool. They just have to drop the idea, without negotiating with any UFC vendors and fighters, and fighters at the end of their contracts would delay resigning. The UFC will pay Dana enough in his current deal to cover Dana's share.