He had to check up because of the car in front of him. Since he was decelerating (even just engine drag especially at high rpm) while getting light over the crest, then having the wheels turned...all ended up getting the car out of shape.
You have to pretty much give up steering, and just get the car slowed down in a straight line, then turn once it's settled after that first hump. You're taught early on that you need to "commit" or "bail" in that part of the track. You can't just slow down and lift.