Trouble with that is, if you show that Barry was never really POTUS you throw 8 years of chaos into the mix all at once.
Everything he signed, every law passed, every legal decision touched becomes null.
Every criminal (legit or not) can challenge their cases and would be able to have them thrown out.
Everything he touched and everything downstream from that blows up on a global scale.
President Trump cannot play that card without destroying everything he is attempting to preserve.
Fruit of the poisoned tree.
Eventually he will face justice. But that is not in the near future.
This war has only just begun.