The most obvious reason is that Canning, who works by the maxim 'I have enough friends, there is a job to do', had created so many enemies that her downfall was inevitable. Her two-year reign saw her replace 80 per cent of the country heads within her remit - including, of course, the chairman and joint CEOs of the UK business. This guarantees that at least a ripple of schadenfreude will disrupt the placid lake of international PR this week.
But CEO Richard Edelman's explanation for ditching Canning's everything-but-the-US role - one which long predated her involvement with the firm - went beyond a breakdown in trust between Canning and the controlling family.
He claims the market has changed so radically that the only way to build non-US business is to export work from the US. Critics of this plan might say that only makes sense if there are people in the non-US management capable of holding onto that business and passing it on. Canning's legacy may prove to be a network of people able to do that.