So Sir Kriss was borrowing the high grade artifact when he used it for his investigation. His sister has to return it after he is done with it, and during the process of using it, there has to be two powerful guards protecting the artifact.
Sir Kriss himself would have acquired more guards to protect it if he didn't want to draw too much attention to the fact that the crown is currently in his possession. That goes to show just how much he values the artifact.
He didn't protect his daughter with two epic beings, but he is willing to spend a lot of money to hire up to five epic beings to guard the crown.
It isn't that he doesn't care about his daughter. It is that he is more willing to risk the loss of his daughter than risk the loss of the high-grade divine artifact.
Despite how much he values the divine artifact, he still brought it out to read Jack's mind and investigate the Golden Hammer gang. This shows just how seriously he takes the Golden Hammer gang.
