Alibaba Group founder Jack Ma, who helped launch China's online retailing boom, stepped down as chairman of the world's biggest e-commerce company Tuesday at a time when its fast-changing industry faces uncertainty amid a US-Chinese tariff war. {"preview_thumbnail":"https://cdn.flowplayer.com/6684a05f-6468-4ecd-87d5-a748773282a3/i/v-i-f…","video_id":"f7d9015a-9d54-4378-b62b-eb602c235947","player_id":"8ca46225-42a2-4245-9c20-7850ae937431","provider":"flowplayer","video":"Top 10 Women Leading Top Companies in Middle East"} Ma, one of China's wealthiest and best-known entrepreneurs, gave up his post on his 55th birthday as part of a succession announced a year ...