After hearing Demon Lord Chong Lou's words, no one dared to say another, be it the Lord of Hell, Ao Changkong, or Yu Shen. As the number one expert on Earth, and by a large margin, his word was law.
No expert present could contend with Demon Lord Chong Lou, let alone speak to him on the same level. Thus, the Black Bear Emperor had to accept reality.
To be honest, if it was possible, he certainly did not want so many experts to participate. He only had nine spots to enter the world. After deducting his own spot, that left eight more.
Once he gave away a spot, there was no way to take it back unless the recipient died.
This meant that the more people there were, the more disadvantageous it would be for him. Furthermore, he had wanted to develop himself secretly, so having the top experts of Earth follow him into the world meant that he would no longer have an advantage compared to them.