The close election along with the various allegations of fraud, be they true or untrue, makes for a pretty good outcome for Trump. He didn't really "lose" - it was stolen from him! Conceding makes him a loser, which would destroy his brand. He'll go to his grave claiming that he won but the Democrats stole it from him.
Considering everything he was up against, I think he can be proud of how he did. Huge turnout, increases in every demographic (except white males LOL). Biden had every card stacked in his favor and just barely eked out a win.