It's also a pivotal moment for a famous media figure trying to climb back up the ladder.
Winfrey's OWN TV network is showing signs of life after a rocky start, and the Armstrong interview offered a chance for many more viewers to check it out.
The interview "showcases the No 1 asset this network has over everybody else -- and that's Oprah Winfrey," said Erik Logan, co-president of the network.
It also showcased about everything else; OWN relentlessly advertised its programming on just about every commercial break.
Winfrey, who hosts Oprah's Master Class, Oprah's Life Class and a weekly interview show on OWN, has been at a real-life television management class over the past three years.
The network launch in 2011 came during the last season of Winfrey's popular syndicated show, and that proved to be a major strategic error.
The daily talk show gave Winfrey's fans their Oprah jolt, and they had little reason to watch the Oprah Winfrey Network.
Winfrey wasn't much of a presence there, anyway. She was concentrating on making sure her syndicated show went out with a flourish.
OWN flailed for direction with little-noticed celebrity reality shows. A Rosie O'Donnell talk show was an expensive flop.
Discovery Communications, which sunk a reported $250m (¤190m) into OWN, told Winfrey she needed to be more involved, on and off screen. In July 2011, she became CEO as well as chairman.
"The initial expectations for this network turned out to be unrealistic," said Brad Adgate, an analyst.
"Oprah wasn't on camera. The shows weren't all that good. The network got raked over the coals. "
The Discovery networks save money by sharing services, yet OWN had set up its own fiefdom.
That ended. Discovery brought in its executives to take over legal and business affairs, and OWN laid off one-fifth of its staff last March.
To the outside world it looked like a sinking ship, while to Discovery the ship was being righted.