McConnell Is on the Losing Side of History — And He Knows It - 2020-09-23
There are two possible reasons why it would be rational for him to act on the Supreme Court vacancy in a way that is so damaging to the reputation of the Senate, and so contemptuous of half of his Senate colleagues and of American voters.
One is that he expects his party to hold power a very long time. Who cares what the opposition thinks when they don't matter now and won't in the future?
The other is that he expects to hold power a very short time, or at least is keenly attuned to this possibility, and believes that once power is lost it is gone indefinitely. Under this scenario, it would make sense to lock in as many gains, as quickly as possible, for as long as possible. The enduring scorn of the opposition is an acceptable price to pay because the long-term contest is essentially over.