Israel's king was Jeroboam I. Judah's king, from David's line, was Rehoboam. Also, with Judah went the bulk of the Levites.
Now, Jeroboam was a politically astute man. I believe the Bible calls him "clever." So he was quick to recognize the possibility that he would lose his kingdom, lose his following, if the people continued to travel south to Jerusalem to keep the Feast. Thus, he made a politically astute move by promoting another religion. Even though it says that "he said in his heart," by no stretch of the imagination does this mean that he invented a "new" religion. What he did was incorporate into his system, and give governmental backing to, already ongoing pagan practices.
But right now we are talking about the fifteenth day of the eighth month, in particular, and the fifteenth day of any month, in general.Remember that we are still, here, talking about Israel (the northern ten tribes) and a very astute political move made by their first king, Jeroboam I—by instituting already ongoing pagan practices as a part of the official governmental policy instituted under him.
What Jeroboam was doing was not just setting up a rival kingdom against Judah, but rather a full-fledged Babylonian religious and governmental system. Once he made the jump into the religious area, it was now set to become part of everyday life. So he had built a new temple, altar, priesthood (with himself as high priest); and, on top of that, he was king. It was dedicated on the very day that the pagan kings designated as a day of homage and sacrifice to their god-kings.
What could he do to keep the people from going down to Jerusalem and having their loyalty shifted back to King Rehoboam through religion? Jeroboam was no dummy—I mean when it came to political things. He was politically astute. He was a real man of the world. He was a very clear practitioner of situation ethics.
Don't get the idea that all of this was done in the blink of an eye. Sometimes the Bible fools us that way because the history that is written is written in such a way to conserve a great deal of space. It appears to us as though Jeroboam just snapped his fingers and issued orders of all these things to be done at once. But the Bible does not say that. These things could have taken months; they could have taken years to evolve into practices that became orthodoxy.
"It is too much for you to go to Jerusalem." Notice this appeal, because here is how idolatry gets started. Make it easier, more convenient, for the people.
