Two causes led to the amalgamation of Christianity with paganism: 1.

The political necessities of the new dynasty; 2.

The policy adopted by the new religion to insure its spread.
1.

Though the Christian party had proved itself sufficiently strong to give a master to the empire, it was never sufficiently strong to destroy its antagonist, paganism.

The issue of the struggle between them was an amalgamation of the principles of both.