Why is it somewhat difficult to distinguish early christian art from other art of that time period?

Well, in the music industry during the 80s  cyndi lauper took a risk in changing a certain type of music art into something creative with her hair dye and wild hairstyles that were bold, her style was entice and screeching that she actually did her get a lot of hate for it because at that time hair dye and crazy patterns wasn't the norm girl's just wanna have fun for example that changed the work of her genre and a lot of people were influenced by her ways. there was other people who took the dare but not a lot. that itself refers to change in art style, because modern times changed. 

Not 100% sure on the answer but i’d say universal as i don’t see why it would be in the definition