Per Bud Crawford after getting nailed w/ a flush shot early in the fight... Crawford told ESPN's Stephen A. Smith that after Spence connected with a looping overhand left in the first two rounds, he thought to himself, "This is it? ... It's going to be a long night for him."
When you're absolutely drained and left everything in training camp just so you can hit the scales, you have no energy or power.
Spence has never been a big puncher, he's always been a guy who's landed in volume and gradually broken guys down. Since he stepped up to world level every single one of his fights, bar one, have gone late because of his lack of one shot power. So not a shock. One thing I noted when they shook hands at the weigh in was just how small Spence's hands were compared to Crawford. So not surprising Bud was the much bigger puncher.
I agree that Spence wasn't the massive puncher that many people made him out to be, but he still had above average pop. He did break Brook and then Ugas's eye socket. But on the night, Spence's power, or lack thereof, didn't give Crawford ANY pause or hesitation.