IDK that the pardon thing is so clear cut.
If Trump doesn't pardon, he is open to Manafort, etal, cooperating fully to reduce jail time. He has no control over the situation in that case.
If he DOES pardon, perhaps Manafort, etal will feel some obligation to minimize the revelations. Again, not necessarily able to steer or control but perhaps Trump will feel some control of the situation. Of course, communicating with Manafort, etal, will be difficult if not impossible without obstruction charges.