It might be interesting to remember that Lübitz worked as a flight attendant (as do many other lufthansa students while they wait their three to five years on a flight deck seat). The new policy would have guaranteed him the alone time to do his job much earlier, and he had already glass cockpit flight experience through his flight training as the lufthansa advanced trainer is a Cessna CJ1. Would have been easy to use that crashe axe and then do what he did now, admittedly easier now, but possible without much of a nuisance back then.
And he was properly vetted, had even undergone the procedure of losing his medical, getting it back due to his psych eval that cleared him again after his depression. Now, cabin crews do not get vetted, have only very rudimentary medical check and a very high percentage of muslims compared to the flight deck crew, not that that has anything to do with the current case. But it might have somewhere else.