Biden may be near his discard date, but do not think for a moment that the Uniparty® will allow for Trump to win the presidency.
They are doing this now for two reasons.
1) If they indict him they won’t have to turn over the document to the GOP. This keeps the document secret. Or if they do turn it over they want to make sure all charges that can possibly be brought are so Biden can pardon his son and everyone else.
2) They want Biden not to run for reelection so they can get another person who they can more easily cheat for. And they won’t be as stupid to tell the world they created the largest voter fraud organization in History.