TikTok Chief Executive Officer Kevin Mayer has left the company after just four months. According to an internal memo sent out Wednesday, the 58-year-old blamed the 'changing political environment' for his abrupt departure. Mayer's resignation comes three weeks after President Trump threatened to ban the video-sharing app in the United States, claiming it may be a national security threat. TikTok - which boasts a whopping 689 million users worldwide - ...