In other words, they controlled part of the Silk Road, which made them rich, powerful, and mean as hell with which to deal.
I read that they were pretty good business people.
I get a kick out of their art. They were verily the embodiment of insecure noveau riche. Their art was a hilarious syncretism of greek, persian, buddhist and hindu influences. I recall a National Geographic photo of a sculpture of a greco-roman aphrodite statuette with a hindu head-dot and buddhist motifs.