According to Reuters, Piëch undertook a cloak-and-dagger campaign to oust Winterkorn as CEO, even after having publicly endorsed the top executive's leadership of the company. Piëch reportedly focused on other members of his family – descendants of Ferdinand Porsche and majority stakeholders in Volkswagen – to install Porsche chief Matthias Mueller as group CEO in Winterkorn's stead. But Piëch failed in his campaign, and was given an ultimatum by the board: either show yourself out or we'll kick you out. And so he resigned.
A big part of Winterkorn's rescue and Piëch's failure reportedly came at the hands of labor representatives on the VW board, like Berthold Huber who was appointed as acting chairman following Piëch's departure. That may leave Winterkorn still in charge, but may leave him beholden to the unions even more than before. Winterkorn has been undertaking a concerted campaign to cut overhead costs at VW, but the trade unions have reportedly been blocking many of the steps the chief exec has proposed.
The next big question is who will ultimately replace Piëch in the long term at the head of the board table. Winterkorn could get the nod, leaving the company to find a new CEO to take his place. Another likely scenario, however, would be another member of the Porsche/Piëch family taking the helm and leaving Winterkorn in place. Whether Ferdinand Piëch ultimately sells his 13.2 percent stake in the company (likely to other members of his family) or holds on to it and exerts influence behind the scenes is an open question.
One way or another, any major appointment at the head of either the management or supervisory board will require support from the Porsche/Piëch family, from the works council of labor representatives and from the state government of Lower Saxony, so the process of filling Piëch's vacancy will likely prove anything but straightforward.