Crocs, perhaps the most polarizing shoe of our time, is making a comeback. The company’s signature foam clog fell out of favor a decade ago, but now it is a star reborn on Twitter and beyond: On the runway, in the pages of Vogue and on feet of people who feel a little funny about it but can no longer resist. The turnaround is no accident, analysts say, but rather the result of four years of strategic changes, following a $200 million investment by private-equity giant Blackstone Group in 2013.