While I know much of what inspired her was the depression she was going through, I thought her knowledge of the illegal acts she knew were carried out also inspired her action. It's been a while since I've read her story though, so I could be misremembering.

Most of what Manning released wasn't exposing crimes. Diplomatic insults via private internal communication aren't particularly actionable.

No, and they weren't intended to be dumped in public. The Guardian journalists published the key for the file containing them, changing it from a leak that a team of journalists were going through to choose what to publish to one everyone had full access to. Manning can't be blamed for that.

Plus, far more of Manning's leaks were about the wars than the diplomatic cables.

Vindictiveness based on non judicial punishment and a failing career.