JKO
Once Zion is Destroyed (M1)
"Once Zion is destroyed, there is no need for me to be here! I must get those codes, and in this mind is the key..."
Well, did Smith in M1 want to return to the source? Or did he already have those premature power-hungry spasms of wanting to take over the Matrix? 😛
He contradicts himself in this scene.... when he appears in M2, he says that he disobeyed and stayed in the matrix... and even though he was there to destroy Neo, it was still different than what he said in M1... anyone follow? 🙂
NEO
Once Zion is Destroyed (M1)
A.I. learining emotions is most likely the cause. Ever notice that programs that study human nature show more human characteristics, and are more likely to go exile. Oracle:Choice, Merv:Causualty and Smith:humans' nomad natures. Note not fall here, these are just the most known. Smith being influenced by Neo is very possible. (See guys, Smiddy isn't so bad once you get to know him.) Since Smith always gives his inevitable and purpose speechs, my guess is he wanted to fufill his Purpose to destroy Zion, and then be deleted. After Neo 'infected' Smith, he didn't want to die(who does?) just like humans. He chose to defy deletion and wandered the Matrix confused. Eventually, he decided since no one excepted him; he would take Purpose away from Neo. As he cloned more and more humans, he took their thoughts and made them his own. After awhile, he wanted to control everything and kill Neo as a bonus.
Or I just wasted all you guys' time. Most likely the latter. Sorry if that was of no help. Sigh, time to return to stocking at Walmart.