“Religious Syncretism” is when various, and sometimes conflicting, religious thoughts are merged together to form a new and often more inclusive faith.
You might think this is a good idea. It would certainly make it possible for people of a variety of religious faiths to “get along.” But while God wants us to “get along,” He’s set firmly against syncretism. Israel was always forbidden to bring elements of other faiths into the one God had given. To do so was nothing short of idolatry because it involved making a religion to suit onself rather than submitting to an approach to God created by God.
More than in any other section of Isaiah, chapters 41-48 opposes the acceptance of other religions and chapter 44 is the most vocal. “There is no other God” but the Lord, Isaiah writes. Mankind will go to astounding lengths to create a god, but in the end, that god is little more than kindling, a god that can neither see nor understand.
The Lord will bring Cyrus to deliver His people, but His people must not confuse Cyrus, the servant of the Lord, with the Lord, nor the gods of Cyrus with the true God of Israel. The Lord is God, and there is no other.