With all due respect, that's conjecture - there's not enough evidence to say why he pulled up the way he did.
Then why did he pull up into an impossible climb that all of us know would end up in a stall? No airliner can go into a 15 degree climb at FL350 and not stall. He either trusted Airbus protections in normal law or was incredibly stupid. I think somewhere in his training he was told you can't stall in normal law so pull it up and let the automation handle it. These two spent most of their careers monitoring autopilots so probably depended on them a lot more than us old timers to fly the airplane.
The cockpit voice recorder shows how confused both pilots were when AS and AP went away. It didn't happen like that years ago before full automation took over.