I suspect a lot of this is about Corbyn not having a clue that he might win till the campaign started, by which time it was too late. He's got a vaguely social democratic reply to austerity and vaguely hits the right notes around that. However there's no real sense of strategy for the game of power. He's running a party that he doesn't really control and even more so, a shadow cabinet he doesn't control. If anything the Blairites have been even more traitorous and willing to put themselves before any chance of winning the next election. Same time, with his mixture of free votes and devolved policy making, he's not really got a mechanism for destroying the fuckers.
I'm aware (I kind) of end up analysing this in the same terms of commentariat, in suggesting he isn't running a very effective 'project'. The bigger problem is that he isn't really building an alternative to westminster projects.