Jeremy Corbyn had an overwhelming victory in the contest for the position of Leader of the Labour Party. He succeeded in persuading the party's electorate that an injection of left-wing policies would make the party a force again in British politics. The fact that Ed Miliband lost the 2015 election decisively on a manifesto which was somewhat to the left of the Blair/Brown era was ignored.
However if the party collectively wishes to commit electoral suicide, so be it. The wheels will come off Corbynmania within weeks, but the true believers will sink their heads in the sand, pretend all is well with the great project and then wonder why they are annihilated at elections.