Gordon Brown was mad, bad, dangerous and beyond redemption. That's what former PM Tony Blair thought, if Lord Mandelson's political memoirs are anything to go by.
So why was Brown tolerated for thirteen years?
Perhaps because much of the Labour front bench was mad, bad and dangerous as well - especially in the final months leading up to the 2010 election.
The "beyond redemption" bit is also relevant. The thing about redemption is that you never know for sure when someone is actually "beyond" it... until of course it's too late, the penny finally drops and you decide: Yep, they are indeed, they truly are... beyond redemption.
It's like a lover who keeps on forgiving a partner, patching things up, splitting up again, getting back... until... eventually... they realise that the lover really is... beyond redemption.
Maybe the people around Brown all thought: he could change. He couldn't.
Still... all's fair in love and war. That's the other reason why Brown lasted for thirteen years. Probably.