He jumped because he was detained, beaten and had his apartment illegally searched. He was under massive pressure, being branded a criminal, and could probably see his career disappearing for losing track of one simple phone.
In a way, Jobs is at fault. Apple is a big chunk of Foxconn's (who he worked for) business. Jobs is so secretive about products, and so vindictive towards companies that leak those secrets, that the security personnel at Foxconn panicked when one of the then-secret iPhones went missing.
I think there are many people at Apple who would jump out the windows, first, before explaining that kind of thing to Steve Jobs... they know their life as they know it, is over... :-)
Well - actually - in China, I don't believe there is anything remotely illegal about having your home searched by authorities... kind of standard operating procedure in such a communist nation.