I think that statement as well as any explains Mahomes's success against the Niners.

There were any number of plays in that game in which the Chiefs could have given up, "mentally". They didn't. The Niners truly do have a 'bully' mentality. They will pound on you relentlessly until you fight back. Once you do... they start making mistakes. The don't 'give up' but their frustration starts to effect their play. It's subtle but if you can not be intimidated you can take advantage of it.