Sometimes a Vice Presidential candidate is not picked to help win an election

Or at least they shouldn't always be picked with an eye on how it affects the chance of winning

Sometimes you pick someone you think will help and they actually do the opposite, so that sort thinking can just be a trap. Now I believe that there were other options for Trump that would have made his ticket stronger than Vance, but as I pointed out yesterday, I think the Donald picked Vance because it was who he wanted to spend the next four years working with if he wins. Vance is big with the MAGA crowd and will certain pump up the excitement level for the base, as if that is needed right now. Now rumor has it that he wanted to pick Doug Burgum, the Governor from North Dakota, but was talked into Vance by Don Jr and Eric. That might be true as well. But I sort of feel like if was looking like an election where Trump needed to use the VP pick and convention to turn things around he would have not gone with Vance. But as it is, the momentum is on his side and this gives him a chance to pick someone he might work better with than he did with Mike Pence. Is there anything really wrong with that? Why does a VP pick have to be little more than an election prop that is cast aside after the election is over?