yep,
there is no explanation why he had so much power on Barbara's husband exepct he telling he can't be rude to people.

Oh my goodness, Uncle Vince was the most annoying, horrible character in the movie! He drove me crazy and I couldn't understand why Jerry put up with him the way he did. Naish did an excellent job in the role, especially if he was trying to make Vince into the most unlikeable person on the planet.
Sweet merciful crap!
It's just tea! sips Needs more gin.

He took no responsibility and yes he was a manipulator. But Jerry was always asking for permission. He was an easy target.
If we can save humanity, we become the caretakers of the world