the evidence, to me, looks pretty solid that Corbyns domestic economic policies are very popular amongst a wide swathe of the electorate far outside the left of the Labour party, but that his foreign, security and defence policies/views are toxic outside the Stop the War Coalition. if he can keep his gob shut about things that offend the electorate then he can make progress, but it appears that that is a political skill he doesn't have, and doesn't appear willing to learn - he did, after, walk into the Argentine Embassy for a chat, and thats what started this. he didn't need to do that, he gained nothing by doing it, and theres no one with even the most limited grasp of politics who couldn't have told him he was on a hiding to nothing - but he did it anyway because its one of his personal bugbears.
politics and winning elections requires discipline and sometimes biting your lip on more minor issues in order to win on bigger ones - Corbyn appears not to have that talent.