Manning was an intelligence analyst, not a sys admin. He leaked materials which were given to him. Under what scenario is it imaginable that someone like Snowden could actually access the things he's mentioned?
Some level of the compartmentalization within this mess has clearly failed. His background is irrelevant to that fact.
The point is, he was in a position to have this information regardless and leaked it. That's the story. Your insinuation that his background has some bearing on the information he has already leaked, the parts those within and without the intelligence community has been able to independently verify and the parts that have been confirmed by the WH is completely speculative.
So if you want to stick to primary sources, we have a PPT wit some logos thrown about in a tacky way.
If he's a Chinese mole, or in cahoots with enemies of the state, it doesn't seem like leaking some slides to the guardian and then filming a confession would be the way to go about it. Is the argument just that he's incompetent/confused, or am I missing something? Genuine question.
Another profession with a bit smaller but much alike level of access is called "janitor".