[Black winter day]

Op can't fold river, cause he is getting close to 3 to 1 and he beats half of villain's possible hands.
I agree, that villain probably c/f AK no d, but he could figure, that he is commited already and that 4th d might scare hero, so why not push?
It's less likely, but the possibility isn't 0.
Since we need only to be right about 27% here and we did get the d we payed on the turn for - i don't fold.
I fold the turn like 75% of the time though vs this villain.