I appreciate all the comments here, but consider another perspective. If there were a federal crime committed (I’m not following the news very closely) and a president can pardon before a trial is performed, then a pardon from Biden would be a total power move. Given that trump would probably either weasel out of the conviction or it would be a slap on the wrist fine, this puts Biden in a position of power over trump. This would also crush trump’s ego if not publicly, it would eat at him in private.