When Ahaz meets up with Tiglath-pileser in Damascus, he notices the rather impressive altar that they have there, and decides to have a replica built back in Jerusalem for himself and the people of Judah. The new altar was designed to look exactly like their neighbours' altar that he had seen in Damascus and, from that point forward, the new altar took pride of place in the Temple and all the daily sacrifices were made there.
Ahaz didn't simply get rid of the Lord's altar, though. He kept it for "seeking guidance," but it was removed from its prominent place at the front of the Temple and moved instead to a less visible place on the north side of the new altar. It wasn't that the altar to Yahweh was REplaced, but it was very clearly DISplaced - moved away from the place that rightly belonged to it.
Like King Ahaz, it can be easy for Christians to want to be just like the people around them - to wear the same clothes, watch the same movies, embrace the same ideologies about gender or about whether all faiths lead to God. No one particularly likes to stand out as being different or controversial; it's easier to go with the flow, be like the people around us and try to fit in.
But, in embracing the lifestyle of the society around them, Christians may be subtly "displacing the true altar." It's not that they reject God or abandon true, biblical faith; rather it's that they move biblical truth and communication with God into the background and give it a place of lesser importance. They still turn to God in an emergency, when they need help or guidance; they still do the Christian thing on a Sunday morning... But on the surface, in most areas of their lives, they look no different from the non-believers around them; they've become a replica of the secular humanists in our modern society.
Displacement leads to drift. Ahaz's actions are a sobering reminder to us to regularly evaluate our lives and make sure that God is truly being given His rightful place and hasn't been subtly shifted to a place of lesser importance.
