One year after NBC assumed the rights from longtime broadcaster ABC, the network is preparing to bring one of the iconic events in sports to a potentially record-setting television audience Sunday. The reasons are many, but the biggest are these: There remain far fewer live events than normal because of the COVID-19 pandemic, none of the 300,000 fans that turn out each year will be there in person, and the event itself still stirs a certain sense of Americana among race fans.