If he weren't too close to the situation to see it clearly, I have no doubt in my mind he'd have thrown in the towel too.
To sit there as an observer, and to see the amount of damage his fighter was taking, any reasonable and responsible person would have pulled their man out.
Wilder knows boxing and as dumb as he sounds sometimes, he's a learned student of the game, he would have been able to see that there was no coming back from the beating he was currently receiving.
He can cry all he wants, but anyone with two brain cells to rub together knows he wouldn't sit there and watch somebody suffer a career and potentially life threatening injury.