Grealish is a quality player, and I think one of those who mixes good ability with a good football intelligence, even though he’s not the brightest outside of sport.
It’s hard to tell 100% from the angles I’ve seen, but it seems to me he was heading in to a crowded area at pace with the intention of going down to try and deceive the ref and get something, He got up quickly was because he could see the situation had developed to villas advantage.
If it was your club you would find plenty of ways to defend him and feel harshly treated but since it’s not....