Time

This demand was actually the greatest reason that Rui was eager to speak to Guildmaster Bradt. Rui knew that the man's powerful distribution network undoubtedly exposed him to information and intelligence that perhaps no organization other than the greatest of intelligence organizations, such as the Beggar's Sect and the Shadow Guild, possessed.

However, Rui also knew that he couldn't simply come forth and ask about the Divine Doctor the moment they met. 

Guildmaster Bradt was very intelligent.

The man would instantly realize what Rui's intentions were and would immediately question whether Rui was even sincere about ascending the throne. That was why Rui decided to generalize his request to the human sages of humanity in general.

This way, he would get what he wanted without giving himself away. It was very understand able that a candidate for Emperor would be interested in getting his hands on the human sages of humanity.