It seems that he was simply stupid and thoughtless. It's doubtful that
he knew that it would "flood the cockpit" with light. People think
lasers will just show a tiny dot even at a great distance.

Previous to his arrest I was thinking that the FBI should put out a
warning that shining lasers into cockpits would result in being charged
with the intent to murder x people (x = however many souls are on
board). But now I'm just shaking my head at his immaturity. He didn't
have the intent to hurt anyone, he was just showing off, not knowing it
was a really bad idea. Something any kid would probably do as well.