Cody Bellinger lost a home run Thursday because he passed Justin Turner on the bases:

Bellinger lined what appeared to be a two-run homer to left-center in the third inning — a ball that hit off the glove of outfielder Raimel Tapia and bounded over the fence.

Turner was on first base at the time and believed the ball was caught. As he retreated to first base, Bellinger passed him in the confusion, prompting umpires to call him out.

ESPN.com

Both runners made a mistake because they thought the ball might be caught. Bellinger ran hard because it might be in the park, and Turner retreated when he saw the ball hit the glove. It’s one of those random events that keeps the game interesting, although in general I don’t think that’s how baseball wants to decrease home runs.