Brother Cat himself didn't expect that his challenge would stir up such excitement. He was only attempting to test his skills and earn some "start-up funding" for his brothers.
It's reasonable that the novice players would rush to watch the spectacle.
After all, with Dog Paddle's announcement on the forum, the player base was still small with relationships among each other generally friendly, so it's understandable that people would come to lend support or quite possibly, wait for a laugh.
What he didn't expect was the massive mobilization of NPCs.
But upon reflection, this was not hard to understand. It had been a month since the disaster struck Cardman City. Those who made it past the most challenging period were now living under a basic order created by Murphy and the players. Entertainment was appealing after so long.