I'm not so sure he's crazy. And if he's acting nutty in prison, it may just be an act to try to get off on an insanity plea. This is an arrogant loner who didn't think he needed anybody, because he believed he was superior to everybody. But his vision of himself was out of synch with reality where he was desperate enough to post online personal ads to get sex (this is a last resort for men who have no other options), where he couldn't get a job or the job he thought he deserved, and where he may have been having problems in school.
He concluded that the only way to get himself the "respect" he thought he was due was to stage this very elaborate attack at the most high-profile event where he could pull it off, the biggest midnight movie opening perhaps in history, something sure to draw nationwide media coverage. Because he believes other human beings are inferior to him, it makes no difference to him if this plan required other people to die. Proving to the world and himself that he had what it takes to have power and control over other people was worth more to him than whatever personal consequences for him that could come from this.
Snips of lyrics from the new Rush album:
The Anarchist, RUSH - Clockwork Angels Album, 2012
http://www.youtube.com/watch?v=on3lLcAz4YU
I lack their smiles and diamonds; I lack their happiness and love
I envy them for all those things, I never got my fair share of ....
The things I’ve always been denied
An early promise that somehow died
A missing part of me that grows around me like a cage
....I plan my vengeance on my own - and I was always alone
Oh - They tried to get me
Oh - they’ll never forget me.