Neo discovers that there have been Zions before, and that he's the product of a systemic flaw in the Matrix. He chooses to go back and save an otherwise-doomed Trinity rather than go the logical path, and therefore sets humanity on course for destruction. The Nebuchadnezzar is destroyed, and the heroes escape, only for Neo to somehow stop the sentinels, raising the possibility of the "real world" not being real at all. The Smith-infected Bane wrecks the defense plan, but ends up in a coma along with Neo. To be continued...
Answer: The script just says "With no choice left, Trinity dives through the window." I think she was pretty resigned to the fact she was going to die and just wanted to go out fighting as long as possible, with the very small possibility that she would survive the fall somehow.
Sierra1 ★