Quote PhillieGirl: I don't get it. Victor use to be Sharon's biggest supporter until he used her to get even with Nikki and now he despises her!!!! Sharon doesn't have a loose screw it is Victor "Mustache" Newman who has a real mental problem~ called Control. ~)
I think the point where Victor turned on her was when she lied to him, and didn't tell him she was going to Kansas to stop Adam's wedding. He vowed that he would let no woman ever make a fool of him, and that's when his vendetta started. If you recall, he also had a vendetta against little blonde Diane when he married her.
Victor married Sharon as a slap in the face to Nikki for being back with Jack.
Victor's sudden disappearance immediately after the wedding, and some sneaky texts that Nikki sent her, pretending to be Victor, put Sharon in a manic state. Tucker saw this and goaded her on to become head of the company as Victor's widow.
Very convoluted story, but the bottom line is, as you said, about CONTROL. When Sharon disobeyed his orders, she became another target for his insanity.
The man has become terribly evil in his old age, and what he can't have, he wants to destroy.