Based on the link provide in post #30:
Ryanair passenger jumps out of emergency exit 'after suffering asthma attack' | Metro News
The issue, as described by the passenger sitting next to him, was asthma.
I doubt any notification from the pilot would have changed his behavior.
I think the more general issue is that not everyone can accurately assess whether they will be able to tolerate the strains of flying. And, of course, there are variations from flight to flight in both the strains and the passenger.
In response to several earlier posts: Perhaps he was not a moron, a clown, or irrational. Perhaps through poor planning he simply got in over his head and needed to depart for his own survival.