I have a feeling that they had not anticipated the level of the competition in Russia, where the cabs were such unbelievable scams that the locals had launched mobile-first services long before Uber entered the market.
Seems like a smart move to me. Given the political situation, operating at scale in Russia is a liability anyway. Now they get some cash and a stake in the Russian controlled operation.
Damn. I used both and Uber is cheaper and <i>much</i> better customer service. Trying to get your money back from Yandex.Taxi is a kafkaesque nightmare.