Video games as a professional sport made no sense to Lars Windhorst, a European oil and agriculture investor, until a summer evening in Seoul. Before him lay an impressive sight: Thousands of kids in lawn chairs outdoors watching teams battle in the 2012 championship for "League of Legends." "It was exotic," Windhorst recalled. Over the next four years, his firm Sapinda Group invested upwards of $40 million in Azubu, a Sherman Oaks start-up developed to stream such e-sports matches online. But in the last year, several employees resigned and the only other major investor clawed back funding, exposing long-simmering troubles inside Azubu.