i had legit forgotten about Shiv's letter to the press, and Ken blowing up Shiv's first presentation as president.
even though i still think part of her decision was a calculation that she could pull Tom's strings, Kendall is what did it.

re-watching her, she sees the vote actually becoming reality you see her reacting in real time. Still i think she was 80/20 in the moment, otherwise she would have voted no on the spot with every bit of confidence and smugness she had.

Ken handled it in the worst way by having a literal tantrum. while no one believes Shiv gives two shits about the dead waiter other than she wanted to play that card as her own nuke, Kendall pretending he made it up was the final straw... it's also when Roman flipped and changed his mind.

they were all such little kids in that room. and really this whole episode.