That word was not an accident. Because he used it more than once to hammer it in:

“I frankly just think it’s hysterical how much the media is overreacting to it,” Vance said while traveling to a campaign rally in Arizona.

…

“So what he said, I thought it was hysterical. I think he pointed out the fundamental chameleon-like nature of Kamala Harris,” Vance said. “She’s flip flopped on every issue. She’s fake. She’s phony. And I think our whole campaign is going to have a very fun time pointing that out. And it sounds like the president kicked us off in stride.”

For those unaware: https://en.wikipedia.org/wiki/Hysteria

The Appalachian hillbilly from suburban Ohio knows what that word means. He went to Yale.