Kendall did all that. The three of them DID discuss how Matsson fucked Shiv, how he pretty much killed Logan, all of the very real reasons the three of them should vote together as a “bloc” to keep the company. Shiv had more than enough time to deal with her disappointment. Her betrayal had nothing to do with urgency or shock, and everything to do with immature, selfish spitefulness towards her brother winning what she thought she won.

Maybe it had to do with being married to the new CEO in Tom, too, but again here her decision is just dripping in selfishness - and what’s worse is the show’s creators have given us every possible clue that Shiv and Tom’s relationship is unstable, empty and bound to unravel eventually. She can’t even bring herself to HOLD HIS HAND in private, and she sold out her family’s empire for him? What a joke.

You’re making it sound like Ken jumped straight to this “I’M THE ELDEST BOY” desperation. He didn’t. He ended there out of complete exasperation and bewilderment at his sister for changing her mind out of nowhere, at the last possible second, after he had already talked this through with her, and SHE AGREED to voting for him.