Shiv is spiteful. There's nothing more to it.
Imagine working for your dad's company from age 22 to age 40 something. Going through every department, becoming VP, CFO, COO then CEO while your sister off in D.C. pretending to be Miss Sloane. Only for her to come back when your dad is about to die talmbout you not fit to be the leader. I woulda been seething too. I been here decades working, fukk you talking about?
Kendall's flaw was thinking he could ever get Shiv and Roman on his side. The jealously was too deep. They'd never support him and he was goofy to think they would.
I do agree that Tom will do a good job though. It's just extremely foul how he got it. I would have preferred Tom beating Kendall fair and square to Shiv backstabbing him