In the first half, the game from Tottenham was not neatly structured, Aston Villa players managed to affect the mentality of Tottenham players with their play and because of that they also hardly got a chance in this match, then in the second half after some improvement in their weaknesses, finally their confidence and cooperation improved so well that they made better opportunities, I don't know what was given by their coach and captain in the second half so that Tottenham's players played much better than the first half, apart from Son's presence, in my opinion there are some strategic gaps used by Aston Villa.
The first half was the best bet for Aston villa to make good use of their opportunities but sadly they couldn't, they lost it and Tottenham didn't fail to punish them in the second half with lots of goals so that they were able to win the game or even share points but the interesting thing has to be in the fact that Tottenham wasn't expected to loose at home, so it's feels to me like a good result, if they were the visiting team they would have had reasons to justify loss and that contributed to their performance too, sons presence usually shows an obvious impact which his absence does too and the second half did made that obvious just like you rightly mentioned.