The buzz of the duel died down a bit after a day, but that was only on the surface, as behind the scenes, many things were already happening, all kickstarted by the fact that not only did Riven win the duel, he dominated, showing unbelievable skill and power that shouldn't be possible with years of training unless he was the hero.
And to add salt to the wound, all investigations showed that Riven had only been at it for a few months and he had reached such heights of strength, it was abnormal, and several theories were being born.
Stories about how he might be using some forbidden techniques and methods. If all of this was merely speculation from sore losers that wanted Image to win, it would have been a simple issue to bury.
But it wasn't. Not only was the Senate invested in it, several other major bodies were also invested and were going about carrying out their investigation.