Misreading Rome

Too often, historians have ignored the sincerity of pagans, misreading their casual forms of worship for indifference. But Rome was far more religious than other societies in the ancient world, and large numbers of Romans, especially those making up the political elite, sincerely believed that the gods had made Rome the great empire that it had become. That being the case, Christianity was an obvious affront to the gods, given that the church denied the existence of the gods and charged that to worship them was blasphemy. It was entirely logical to assume that for Rome to tolerate Christianity was to risk bringing down the displeasure of the gods upon its affairs.— The Triumph of Christianity, pages 140-141

<idle musing>
The Romans had a "I give that you will give to me" (do ut des in Latin) attitude towards the gods. They firmly believed in oracles and omens—you could say they were "superstitious" to the extreme; the world was full of gods. The early Christians were called atheists because they only believed in one god. That upset the balance of power dramatically in the mind of the Romans; they didn't know how to handle it, so they worked to eliminate it...if it itches, scratch it!
</idle musing>