This isn't that complicated. Conor McGregor is about money. Honor, integrity, Respect, that's all bullshit to him. Those same things are what Nurmagomedov's life is built on.
McGregor insulted a man's father and religion, then got in a cage with that man, and got beaten so long and so badly and so completely he actually tried to tell that man "It's just business" DURING the fight. To me, that's cowardice. To McGregor, it's the truth.
The next big payday for McGregor is Nurmagomedov again, only Nurmagomedov has no reason to give him that fight. So McGregor ups the insult game, figuring Nurmagomedov.
Here's a novel idea I offer to Nurmagomedov. Agree to fight McGregor. With the stipulation that McGregor get NOTHING if he loses. McGregor says he doesn't need the money. But the only thing he respects is money. So let the UFC give him a reason to try and win.