If Trump fired Mueller in reaction to all this, he would take a matter that now is at the edges of his world — Manafort has already been gingerly tossed under the bus, and no one knows Papadopoulos —and make it a truly all-consuming crisis. And for what? As a practical matter, there is no way to end the investigation. If Mueller is dismissed, all the special counsel’s materials will presumably be handed over to Congress, and he would, at some point, be a lead witness in impeachment hearings.
The option of pre-emptively pardoning everyone targeted by Mueller also is foolhardy. A Trump pardon of Manafort would associate the president with the lobbyist’s alleged malfeasance when the point should be to establish distance, and would convince everyone that Trump has something explosive to hide.
The calculus here isn’t complicated. If Trump is guilty of serious wrongdoing, there is nothing he can do to stop it from being uncovered. If, on the other hand, he’s innocent, firing Mueller would be a catastrophic error.