It's everyone else's fault..... Corbyn says so (Taken from what he said in The Observer"):-

"I am proud that on austerity, on corporate power, on inequality and on the climate emergency we have won the arguments and rewritten the terms of political debate.

There is no doubt that our policies are popular, from public ownership of rail and key utilities to a massive house-building programme and a pay rise for millions."

I dunno, words fail ya?