Sensitive individuals should have gleaned enough by then that the competition is very important to the racial council. Why would they change an ancient tradition of their race for a simple competition? Unfortunately, it still wasn't enough. If Soverick's intention to attend the competition wasn't announced, then the number of participants wouldn't have been up to a million at all. Soverick's notoriety and popularity drew the largest number of participants to the competition.
Soverick's very attendance was needed to bring in people. Even then, they came to gang up on him and beat him up, not to support him like the Vipers supported their paragons. It all culminated in that final battle of the 3rd challenge. The serpentine world god also didn't tell his people about who their enemies would be or the purpose of the competition, but he didn't need to. He called the competition a training session, and Vipers flocked to attend just for the honor of it.