If established researcher in the field makes a breakthrough of this magnitude I would expect rumors to start to circulating first. Showing the draft to few colleagues to see if they can spot mistakes before 'shaking the world' is probably a good idea.
If he publishes without consulting peers:
If his proof is correct, he gets unending fame, millions in prize money.
If his proof is laughably flawed, he'll promptly be forgotten as one of the 100s who have been wrong before him.
If he consults his peers: If his proof is correct, he may end up sharing credit, maybe they'll even publish his work quietly under their own name while he's still waiting for feedback. Maybe that is what we are reading now.
If his proof is laughably flawed, then they'll give him his feedback and only his peers, instead of the whole internet will laugh at him for a day, before it's all forgotten.
Seems like with any tiny chance of a correct proof, the dominant strategy is, by far, to publish without consulting your peers.