If Trump loses in 2024, Vance would be the principle reason in a close election. Vance did not bring any additional voters to Trump. OTOH if Trump wins in 2024, Vance is best to carry MAGA forward.
Trump could win without Vance... But Vance will fit in nicely for 28 and 32, with his youthfulness and military experience.
You are wrong.
Vance is bringing the people that everyone over looks. The "hillbillies". Even though some of them live in cities. Not the welfare poor. The working poor. For the first time in a long time someone on the national stage is seeing them.
They want their children to be able to go to schools will give them a better education then they had. They want to be able to heat their houses and put food on the table. They would like to have an honest shot at climbing the ladder rather then having it kicked away in favor of other people because they are "privileged".
They are the Invisible men.
They are not switching parties. These are people who never voted at all. These are truly new voters.