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?

A scenario beyond your imagination has no less of a probability of occurring than one within it. You don't know (and neither do I) what system(s) he had access to and what type of data he acquired. You're assuming the NSA actually uses certain technologies it has at its disposal and it does so appropriately with no means of proving that assertion. You're also ignoring that the NSA isn't a single "entity". It's instead a very large bureaucracy with countless independent workers, contractors, sub-contractors, assistants, analysts and, yes, even sys-admins.

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.

What he leaked is a slideshow. The rest of what he said has been received by many here as gospel, when in fact, there are legitimate questions about his truthfulness.

So if you want to stick to primary sources, we have a PPT wit some logos thrown about in a tacky way.

What's his incentive for lying? I totally understand being a skeptical that a relatively low level contractor got access to everything, but I don't understand what would motivate someone to go public and incite the wrath of us intelligence if he didn't at least believe he was telling the truth.

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.

Didn't he also leak the verizon metadata story which was confirmed true by various senators?

"System admin" is the professional who get the hightest level of access to your computers, so he can keep them working. Most times even the people with physical access to your datacenter (AKA, the people that can get any data you have) have that same title.

Another profession with a bit smaller but much alike level of access is called "janitor".

Sysadmins generally have the highest levels of privilege on any given system. I've worked in and around sysadmins in some very large firms and when you're responsible for things like server installation, maintenance, and backups, it's very rare that you don't have access to all of the information on them.

While my experience is limited, the system administrators I have worked with typically had more rights on the servers I worked on then I did myself. I do not find it at all surprising that a system administrator at the NSA might have access to some of these systems or a clear route through which to attain such access.