Holy shit that hurts.
I track with Kitou's line of thinking that Sofue probably flipped on Kirishima because Noguchi let spill that he would lose, and gave a BS reason about Kirishima not showing enough deference just to save face. Even Ooshima didn't vote for Kirishima after seeing Katou's near-unanimous selection, and you can see how unhappy all of the other, non-professor doctors are to have cast their lot with the loser. No one in this setting wants to be associated with the loser.