A coerced guilty plea isn't an admission, it's a false confession. Is there any admission other than a coerced plea deal?
From what I understand, Manning only sent part of a password hash and didn't say where it was from, so if Assange had attempted to crack the password then it would've been a failed attempt and he wouldn't have known what the password was for. Manning already had legitimate access to all of the databases from which she downloaded data, logging into another user account using a cracked password wouldn't have provided her with more access than she already possessed. Furthermore, the US government had no clear evidence that Assange was the person behind the 'Nathaniel Frank' username who Manning was communicating with.
It's possible the US government just wanted to make an example out of him for daring to expose US war crimes, and that the computer hacking allegations had no real merit. I have no idea if he was innocent or guilty, but obviously a lot of people are biased because they don't agree with what he did.