There seems to be an acceptance that the Labour Party in its current state is, to be gentle, unlikely to command a majority any time soon. On here anyrate, and polls, (yeah, I know), seem to back this up.
To this observer without a dog in the fight, why dont the Labour Party ask themselves why? Instead of their core support telling everyone else who isnt a paid up member, that they are wrong?
Or have I missed something?
You haven't missed anything, except that the your question was asked and answered in the summer of 2015.
The people who lost that leadership election were the factions at the top of the party who had lost the two previous General Elections, who lost Scotland, who built most of the groundwork for losing the other heartlands, who lost more than half of the party membership and who put the party millions of pounds into debt. People wanted change, the party needed change, the voters had just rejected them because they hadn't changed (from 2010 at least) and yet the only option on that ballot for actual change was Corbyn - which is probably why he won in such a landslide.
The people at the top of Labour could have recognized that and engaged with it. They could have at least saw that getting smashed by a nearly 70 year old bloke and a hastily assembled network of supporters might suggest that they had a problem. Instead only a very few of them did either of those, whilst most instead either sat it out, or openly attacked the leadership, all with the hope of putting themselves back in charge.
The result is of course what we have seen since the referendum result, which is open (and largely one-way) warfare, chaos and a Tory Party that thinks this is a golden opportunity to screw us all.