Don't let it bother you, those kinds of contests are very often rigged, especially when money's involved. Even if they're not, they overwhelmingly depend on luck rather than skill.
Some might say to cut your losses, but honestly I don't think you have any. Time spent honing your gamedev skills and making a good game is not time lost. So uh cut your winnings I guess? And keep at it. Don't enter gamejams with the intention of winning, enter them to make a great game. Winning is just the cherry ontop.