A big part of it is that his main priority is not to win over voters, it is to reshape the Labour Party. If he leads for four and a bit years, loses a few more seats but successfully removes the left of the party and encourages right wing donors, sufficiently so that his successor is as right wing as him, he'll consider his term successful. I'm not convinced he remotely knows how to do that though, based on his actions so far, so what's actually gonna happen I imagine is he'll fail miserably in every regard and the next leader will be a compromise candidate like Ed Miliband was.