So what happened to the Lib Dems & Menzies ... a coup or is there something else ?

I think a bit of both. I genuinely think he is too old. I don't wish to sound ageist but the election needed to happen sooner rather than later for him and would he really want all that hard work at 69? My old man's looking to retire at 60!
They should get that guy in who dates the Cheeky Girl. They're always good for a laugh are the Liberals.

He was the Iain Duncan Cough of the Lib Dems. He may have had ideas, but leaders don't need ideas (they can delegate that task to the conference/spin doctors/opposition parties). Leaders need the ability to inspire and motivate, and he didn't have that.

I think that he was also conspicuously lacking any sense of humour; if he'd been able to come up with a few self-deprecating jokes about his age, he could have turned it to his advantage.