Why the German 'big four' are committed to Formula E

Formula E is only in its fifth season, but there are plenty of big names on the grid. Audi and BMW already have factory-backed operations, while Mercedes-Benz will join next year. Motorsports juggernaut Porsche will also join the grid in 2019/2020. The Renault-Nissan-Mitsubishi Alliance and Mahindra have been on board since day one, too.