I think there are two answers to this. First, there is a long standing tradition in the US that the new guy doesn’t put the old guy in jail.

Look at so many other countries and so much of world history to see how that style of governing is problematic to the transfer of power from one regime to the next and why it causes its own set of problems.

The second, and arguably the most important, is that the American people as a whole can elect whoever the fuck they want to be president, no matter what any mid level beurocrat, judge, lawmaker or even current president or other official says about the issue, even if said person is in jail at the time.

The law and its punishments should still apply to all, including the president and former presidents, however.