Or (c) that any future administration is going to have a lot of more pressing concerns that will drown out seriously relitigating past mergers and acquisitions,

Or (c) that any future administration is going to have a lot of more pressing concerns that will drown out seriously relitigating past mergers and acquisitions, and any concerns they do have will most likely be mollified with agreed remedies that sacrifice far less than the value of doing the merger. Very few administrations do everything they theoretically could under the law and their own guidelines (even the ones that also do lots that violates both.)