Because King Bai was still around, his statue was sealed. Treasure seekers would have to wait until he had passed away before his statue was revealed in the Pavilion.
The statue wasn't being shown right then to avoid giving his children the opportunity to crack the statue. Why that would have been a bad thing, the stone didn't say. As a result, Han Sen didn't understand.
The last king before King Bai was called King Bao. Not much was written about him, just a few words that looked like default-text instead. He had beaten a race and expanded the breadth of the Extreme King's domain, but the name of the race he had beaten wasn't even listed.
The expanse controlled by the Extreme King had been maximized during the reign of King Bao, so there wasn't much room left for them to develop nowadays unless they could defeat the Very High or Ancient God. There was nothing else King Bai could do.