What is wrong with Vance?
Look at Nate Silver's prediction, while the electoral count looks nice, it is still 131 days until the election. The vote count is actually in favor of Biden. That means a few states on the fence. Trump needs someone that adds votes push up the count to secure more states.
That is why I and some others support Gabbard. She checks off a lot of boxes, is aligned with Trump, and would absolutely add votes--independents and democrats. No other VP candidate offers as much to help Trump beyond his base.