I doubt that Vince can say what decided it for him. Slowly the shift occurred, and doubts started to creep in even further, because Vince did have doubts from the start. He didn't buy the 19 Arabs with box cutters directed by a guy using a cell phone in a cave in Afghanistan.
I think I get it, because evolution is similar for me. I read ID books and just could never see how evolution worked, how this all came together. But ultimately, it did. At some point you realize that God is not orchestrating each and every mutation. Yes, mutations don't often occur to the good, but sometimes they do, and somehow maybe the mechanism isn't completely understood, but ultimately it is the only explanation. Doesn't mean there is no God.
Just like the planes really did hit the WTC towers, the 2 tall ones.
So I get it. I believe in evolution, but can't tell you when I started. It was incremental. At some point the evidence becomes overwhelming and the alternatives .. are left wanting.