Question about Julian ange supplier?

He leaked lot of doents per news reports. But it still does not make him the leaker. It was leaked by the person(s) who supplied him the doents. And I don't think one person alone can supply 250,000 emby cables. Manning didn't even work in any emby and it is next to impossible for him to leak such mive data single-handedly. Can there be possibility that Manning is a scapegoat for someone else's actions? Maybe the person ranks high in chain of command, and so the lowest level people like manning are picked? Also they do not focus on who handed ange the data. They are only focusing on ange and wiki-leaks. Why? It should be the other way around.