Timing beats speed, Brook KOs Khan all day every day and twice on Sundays.
Khan has a bigger following and he pulls in viewers with his exciting or 'prone to be KO'd at any time' style. He's been in some very entertaining fights over the years but has a boxing IQ of zero, he isn't able to adapt at all, it's as though he's learning nothing from his opponent because you see him getting caught with the same shots in round 10-11 that he was getting caught with in round 1 and 2.
Eddie Hearn knows Khan still pulls in the numbers, he signed him for 3 fights, the first 2 were tomato cans - Khan typically makes tough work of last nights, who really isn't anywhere near elite level. This was all building up to the 3rd fight, and I think it was clear from his comments that he wants Pacquaio not Brook.
I know some of Khans mates and some of the places he hangs about, he's never taken boxing seriously, he smokes far too much shisha and if he lost to Brook he wouldn't be able to show his face in certain places. Whereas if he lost to Pacquaio he can carry on boasting about how he has a better resume than Brook