Eye injuries doesn't effect your punch resistance and get you hurt, eye damage would've been later in the rounds and swelling, this would've effected his mental fears.
That one shot he just didn't see coming and got hurt, that's all.
Now iff the fight went on and the eye was damaged and swelled up and pain, then vision problems started and then Brooks just quit then you have a case that nobody could contradict.
That's not what happened, Brooks was looking good and beating Crawford until Crawford adjusted and slipped the jab then caught Brooks with a hook/jab that Brooks stepped into and was staggered, hurt badly, then Crawford just finished him, we see this all the time especially with smart powerful gifted Boxers with high ring I.Q, like Crawford who's knocked percentage is very high and I don't believe Spence hits as hard as Crawford but his pressure and acclimation stops his opponents, there's video evidence of this against lesser competition, when Spence first started, but Crawford has shown us that he's a superior puncher throughout his career.