What you were told to believe were interpretations of doctrines and scripture based on creeds developed and adopted over the centuries by the religious and political elite.

This is surprising but it makes sense. Even before the internet, almost everything that people learn (except that in education) such as in news and entertainment are influenced by what seemed to have the largest control of money and power (i.g. political and religious elites).

Going to what's happening now. We seem to have a chance to finally be able to get away from those influences as easily with internet and decentralization, and thus, have more diverse knowledge.

As for the reason why, I'm not sure. Maybe it's god's/gods' works or just how humans evolve naturally with increasing complexity through time. All I'm sure of is that we're going to that direction.