After Christianity gained dominance in the Roman Empire, it became clear that they regarded their God as very authoritarian in nature - and as a result, they proceeded to imitate their God and become exceptionally authoritarian themselves. Controlling society, they ruthlessly exterminated other religious beliefs, with only Judaism being permitted to co-exist with their own One True Faith. The exclusivist ideology which fostered such attitudes has continued on through today, with little alteration.
Pagan religion was first prohibited wholesale in 392 by emperor Theodosius. Heavy financial penalities were enacted, but it was not initially very effective. In Theodosius' code it was written:
We command that those persons who follow this rule shall embrace the name of Catholic Christians. The rest, however, whom We adjudge demented and insane, shall sustain the infamy of heretical dogmas, their meeting places shall not receive the name of churches, and they shall be smitten first by divine vengeance and secondly by the retributions of Our own initiative, which We shall assume in accordance with the divine judgment.
And later, with regards to Pagan buildings:
We command that all their fanes, temples, and shrines, if even now any remain entire, shall be destroyed by the command of the magistrates, and shall be purified by the erection of th sign of the venerable Christian religion.
This resulted in further legislation, culminating in the death penalty for non-Christians in 435. All citizens had to belong to the official "Catholic" Christianity - the only other permitted religion was Judaism, and Jews were isolated as much as possible from the rest of the population. As the geopolitical and military position of the failing Roman Empire gradually deteriorated, people readily turned towards the activity of trying to appease God - a reaction which is not unknown in contemporary society. Between 429 and 439 about 150 different laws were passed defining and defending the "Catholic faith." Church lands became exempt from taxation and bishops became immune to any sort of secular oversight or punishment.