I'm not sure if he ever visited Jordan although he traveled the Near East in his youth and was friends with Herod.
So it might be that the people of Jerash would have honored him with some games, even in absentia.
But really, I'm sure the reason for the 'honoring' of Julius Caesar is that the tourists probably don't have any clue about any other Roman rulers.
Yeah, that last is probably dead-on. The Romans had to conquer the region.
King Herod the Great
http://www.livius.org/he-hg/herodians/herod_the_great01.html