It doesn't make sense. If the endgame for Uber is self driving cars they'd have much longer runway if they were a startup doing only that, instead of bleeding money on both ends. They were originally an app company from the time when an app gave you easy access to capital. It's more likely the self driving thing was something they had to do to keep the high valuation as a tech company. It was probably an easy pick since it's something in vogue not too far from their normal business.