By all means, admire the goal. But it’s posted here for the keeper’s footwork. When Villa first takes the shot, the keeper does the correct thing: he turns his hips (the dropstep), and runs while keeping his eye on the ball. Perhaps inexplicably, however, within a few yards of the goal, he (re)squares his hips and backpedals. When he makes a play for the ball, then, he jumps with his calves (because of the backpedal) rather than with his quads (which he would have / could have from the dropstep; and, of course, the quads are much bigger than the calves and are the muscles that generate jumping power).
I suspect, after watching it a few times, that he resquares his hips because he anticipates catching it, i.e. he squares to the ball so he can catch it facing forward, exactly what he should have done. Whether because of misjudgment, however, or a sudden gust of wind, the ball carries farther than he anticipates and he is no longer positioned to catch it. He makes a somewhat feeble attempt at parrying it (better, to be honest, than expected, given that he jumps from his calves), but is now out of position, and the ball finds its way under the bar.
If he had continued running the way he first did, I suspect he would have been able to parry it successfully: worst case scenario is a corner kick. But by resquaring his hips, whether well-intended or not, he makes it difficult (and in this case impossible) for him to catch the ball and prevent the goal.
Take a look for yourself and see what you think.
ScreenFlow from Ed DeHoratius on Vimeo.