The surprise resignation of ByteDance founder Zhang Yiming as chief executive has left many unanswered questions at the tech unicorn, not the least being "why now" and "what's next" for the company behind hit short video-sharing apps Tik Tok and Douyin. Perhaps the most intriguing question is whether Zhang, who created ByteDance in a Beijing residential flat nine years ago, will remain the de facto boss after he officially cedes day-to-day.