Like when Tua and Ibeabuci threw 1000 punches each against each other.
Usyk is known for his insane stamina and he's a small heavyweight but these guys were 250lb muscle behemoths and threw more shots than Usyk and neither even really got that tired.
Why was that?
They had great chins and could allow themselves to get hit by a few to land a few.
Usyk can't allow himself to be hit that much by men much bigger than him.