I’m thinking along the lines of Moderator 80. The Tanchuma (Balak 4 the yesh omrim) says that all the kings would go to him for advice. So essentially Bilaam was somewhat of a leader for the nations. Its possible that they looked up to Bilaam because he was a reflection of them.
Had the nations wanted to know what Hashem wanted from them Bilaam could have told them (as we see in perek 22).