Over the past few weeks, users of the video app TikTok braced themselves for a national ban to take effect.This weekend, the app went dark. But less than 24 hours later, it came back. And it credited President-elect Donald J. Trump with flicking the switch.Sapna Maheshwari, who covers TikTok for The Times, discusses the biggest social media ban in American history — and whether the incoming president can actually stop it.Guests: Sapna Maheshwari, a reporter covering TikTok, technology and emerging media companies for The New York Times.Background reading: