There's far too much noise, too much motion and panic and anger and all-around chaos, for Greg to keep up with any of it. He just keeps gripping the wheel, white-knuckled and trying to grasp what little illusion of control he's got. It's when Steven and Amethyst climb out of the van that he pings in to what's happening.

"W-wait, Steven, what're you gonnaaaaaAAA CATCH THE VAN CATCH THE VAN"

The burst bubble leaves nothing keeping them aloft, and the shockwave of fusion gives them a head start down. Greg floors the gas, praying for an even landing.