Crucifixion was seen as very degrading. It was primarily used against slaves and lower classes. It was also extremely brutal and excruciating. Some commentators said it was worse than being burned alive.
Since Roman citizens were exempt from crucifixion and upper classes were permitted other, less horrible forms of execution for crimes which were not against Rome, all that was left was pretty much peasant Jewish classes who committed crimes against Rome.
Just to make this clear- Jannaeus was a Hasmonean Jewish king, not a Roman. You are comparing a pre-Roman regime to a Roman one. That’s why I used the Salem witch analogy.