Because some prick changed the rules as to how leaders are elected. Instead of an electoral college which weighted the PLP, the unions and the membership at one third each they changed it to a flat one member one vote. This means some beardy **** who has just walked in off the street has as big a say in the leadership election as any Labour MP.
It wasn't Ed himself that changed the rules but I think he was largely responsible for triggering the review that proposed the change.
So now 100,000 beardy ****s join up just before a leadership election and vote in another beardy ****. The party is effectively ****ed.
Burney Would probably argue that it is democracy at work and that the PLP has forced a centrist leadership on a grass roots left wing party for a century. He would also piss himself laughing at what an utter mess it is