The Superbowl thing was pretty clearly a publicity stunt gone wrong. Makes a lot more sense being planned by Jackson’s side vs Timberlake’s.
And so what if he bragged about being her first? She dumped him pretty publicly. Everyone knew it at the time. The “Cry Me A River” music video was revenge for that whole situation, and the public ate it up because we all knew she did him wrong. It kick-started his solo career.