You both had similar ratings and you probably had equal chances of making blunders. Your opponent happened to make the fatal mistake and you didn't. That's all
The game was just really low quality in general
Other than missing 5...Bxg4 black played fairly solid good job, try to do an even better job next time.
1200s, and 1300s play practically at the same skill level. The lower the ratings of the players the larger the gap that is needed to be of significance.
@lurarose mistakes at 10,11,13 gained 3 pieces
Yes yes, I see you won a mountain of material.
17... Qe3# would have wrapped it up 14 moves sooner