For two decades Turnbull has been known as a leading republican. His seat, Wentworth, includes the centre of Sydney's gay and lesbian community. As a minister in the Howard government he had led moves to acknowledge the urgency of acting to mitigate climate change. None of this was a secret. His stances on republicanism, gay marriage, and climate change are, or were, a logical, rational consequence.

Tony Abbott was right when he pointed out the Turnbull government had changed almost none of his government's policies. The change of leadership, by implication, had been unnecessary because it changed nothing of substance.

The Liberal Party, which likes to think of itself as the natural party of government (NPG), made Turnbull leader on the strict condition that he was not allowed to lead. Previous leaders of the NPG were allowed to do pretty much as they liked. Not Turnbull. Instead of the centrist policies that his reputation with voters was built on – the same reputation the NPG was relying on to get it re-elected, remember – he was given a warmed-over set of right-wing policies and broken promises to sell, the same steaming pile of junk that had made his predecessor so disastrously unpopular that he had to be dumped just two years after he won power.

But what undermined him fatally before any of that, was a separate lack of judgment for which he is less to blame.

Turnbull is not exactly renowned for an ability to disguise his feelings, but the natural party of government seems to have figured that no one would notice if he abandoned two whole decades of his life's work, that Turnbull would readily manage to conceal his predicament from the rest of the country, and that he could convince people he had become nothing more than Abbott Lite. Being the natural party of government apparently gives you the ability to misread your own colleagues, defy reality and ignore human nature with absolutely unshakeable confidence.

Turnbull, of course, did not improve his own chances by making the series of unforced errors already mentioned. But they only added to the air of falseness that his NPG colleagues had hung around his neck, the dead albatross of his abandoned centrist program. They didn't create it.

Once the idea had been planted in voters' minds that Turnbull in 2016 was no longer what he had been, that he was now only an empty simulacrum of Abbott, he was fatally undermined. When Bill Shorten, with the flimsiest evidence, accused him of wanting to privatise Medicare, Turnbull's denials lacked credibility, because he himself had been forced to exchange his own credibility in return for the leadership.

Voters could see the falseness of Turnbull's situation; astonishingly, the NPG could not. We can guess how confident the NPG's ultras must have been from the strength of their reaction now everything has turned to custard. It can't possibly be their fault, we hear them telling themselves.

Turnbull's to blame. He hasn't delivered. He's a failure. He ignored the NPG's base. Everyone has always known he was flaky. Time to start undermining him. Time to bring Tony Abbott back. People have turned to Labor, in the NPG's mind, because Turnbull prevented them from enjoying the full benefit of Abbott's rich and inviting policy legacy. It doesn't take much to foresee another NPG master stroke in the making.