It's just a theory, but Maxos could have reached his purpose and become kind of omniscient. With so much power, so much knowledge, what does he have left? the opportunity to share it at the price he wishes. I think challenges could feed his curiosity about how-this-one-is-going-to-act type of questions, since it's the only thing he wouldn't know.
Well, I'm probably not right, but it would make (some) sense according to me.
