Two things:
1) He will never recover from Trump calling him “Rat Face, with the teeth, and the beady eyes” during the election when Sasse came out as a Never Trumper.
2) He suffers under the delusion that if Trump had submitted a female nominee, the Dems would not have attacked her with just as much ferocity as they did BK. He forgets Sarah Palin. The entire reasoning behind his advice to Trump to nominate a woman was to shrink from the enemy and try to appease them, in a move very reminiscent of Chamberlain and the Nazis prior to WWII. It strikes me as almost too good to be true that Flake is named “Flake,” and Sasse looks exactly like a rat (or weasel, take your pick). Perhaps Divine humor at play...