BG is the classic case of someone who needed that initial win to gain his confidence. So often in previous Tours he was there or thereabouts but rarely committing fully to the move.
Now he knows he can do it, he’s gained the respect of the peloton which allows him fractionally more elbow room and he and the team believe he can do it. So he does it.
Plus he sounds so lovely in his interviews, like he’s still in a dream state and can’t quite believe what he’s doing, like he’s afraid he’ll wake up at any moment. Bless him.