When NBCUniversal launched its streaming service, Peacock, in 2020, it had a rocky start. Now it's trying to regain its footing by live-streaming the Winter Olympics, along with new shows and movies. As WSJ's Lillian Rizzo explains, the stakes are high for NBC and its parent company, Comcast, to get it right. Learn more about your ad choices. Visit megaphone.fm/adchoices