When Uber Technologies Inc. went public on Thursday, investor Bill Gurley received one of the biggest personal payouts in venture capital history: an amount estimated to be more than $600 million, according to data compiled by Bloomberg. But the path to that payday was neither obvious nor easy, and included the purge of the company’s fiery founder and chief executive officer, Travis Kalanick. Gurley’s crusade to oust Kalanick was highly unusual. Venture investors’ success depends on their ability to convince entrepreneurs to sell them equity in their startup.