Why did Romans respect ancient religions?
The Romans, themselves steeped in paganism and mythology, respected other religions when those faiths were ancient, because such religions existed before Rome did. Judaism qualified as ancient, so Rome generally granted it freedom and even protected temple tithes. Christianity was viewed as new and also proclaimed a king with power above Rome.
Les explains that the Romans were steeped in paganism and mythology, so they had respect for anyone else's religion if it was ancient. A faith going back into antiquity was respected because it existed before Rome did. That is why the Roman Empire generally gave the Jewish religious people freedom, allowed tithes and offerings to flow to the temple from across the empire, and even gave them safe protection. By contrast, Christianity was thought to be relatively new, and it claimed a king with power above Rome, which infuriated them.