Why Vance? He does nothing for Trump politically, he already has the good old boy, Merica first voter. Ohio is a lock. Little help in Pennsylvania, maybe. Nothing else.
Vance has made quite the shift from Trump is America's Hitler to where he is now. Was he full of shit then, or full of shit now? Did he grow and learn, or just an opportunist? Trying to spin this as a positive seems like a uphill battle, and again, gains them no votes that I can see, which brings us to my take.
Trump is certain of his chances for victory and with good reason. He was up strong pre assassination attempt, and now has warrior God status. It's a lock. What Trump wants is loyalty, blind loyalty. Vance offers that. How to be sure? It's in is upbringing, loyal to family no matter what. Read the book, watch the movie.
Vance will be family. Most importantly he'll never offer critique. Trump hates critique. Criticism? He loves it, thrives on it, the more vicious the better. It gives him the chance to be his true self. But critique, honest trying to be helpful critique? He takes that as an insult. You dare question the Donald. Vance is a yes sir, follow orders, get it done for the boss kinda guy. It's who he is and that's why he's the VP.