The founder of Russia’s leading social media network—a wunderkind often described as Russia’s Mark Zuckerberg—has left his post as CEO and fled the country as cronies of President Vladimir Putin have made steady inroads into the company’s ownership. The slow-motion ouster of Pavel Durov from the network known as VKontakte, or “In Contact,” is the latest sign that independent media outlets in Russia have become increasingly imperiled. Although months in the making, the loss of Durov’s leadership in VKontakte means that the space for free speech on the Russian web could shrink even further. …