0:51 - 1:42 In the first game, he sacrificed the Knight, Bishop, and the Rook and checkmated his opponent perfectly! This is what we call perfect sacrifices!
I get the feeling in the first match the black did a huge mistake castling kings side when he was so undeveloped and white was having a lot of pressure that side. The moment that the white saw that castle decided to go instantly for the checkmate. I don't know much about chess so I might be wrong. What I would do in that case would be to start trying to castle Queen side though.