William Morrison is one of the top players in Maryland. He is nicknamed "The Exterminator" for his "ability to process lower-rated opponents" (I read that somewhere). I presume that means he grinds them up like a food processor and points come out the other end. Although rated 2509 at the time of this game, we all know that a player's rating is just an average measure of his ability to play all types of positions. A player can play some positions like a GM if he really studies and understands them. He can also play well below his rating if he is just making moves without a plan and waiting for mistakes from his opponent. I think that is what happened in this game.
White didn't play any brilliant moves in this game, just as Black did not commit any blunders. But White, from much experience with this opening, stuck to a plan of maximizing his one advantage (his kingside majority of pawns), while Black did not do the same on the queenside until it was much too late. He also failed to trade off a key White piece (the rook), which dominated the endgame and was poised to deliver mate at the end.
The point is that, no matter what your rating is, you can be a master of a given opening or position through study. Players with high ratings have mastered more of these positions than you have. But once in a while you might get lucky and get into a position that you have mastered and they have not. When that happens, they are in for an unpleasant surprise!