Well, I don't find it too strange to assume that Golota himself would know why he deliberately fouled his way to two DQ losses, in two fights that he was clearly winning.
Let's take it match by match:
1. McCall vs Tyson
2. McCall vs Mercer
3. Mercer vs Tyson
I actually think McCall has the best chin. When he fought Lewis the second time, Lewis caught him with huge uppercuts and overhand rights (Lewis' trademark punch) and he didn't even blink. Maybe the crack made him "invulnerable".
I have only seen McCall against Lewis. Do you think his ability to take a punch was affected by crack? The reason I'm asking is because I couldn't believe the shots he was taking from Lewis with his hands down - particularly those uppercuts.