“are a deception.” The Hebrew word for “deception” is sheqer (#08267 שֶׁקֶר), and it means lie, deception, fraud. The people went up on the mountains to worship their idols (idol temples and worship sites were often on the top of mountains, just like Solomon built worship sites, likely small temples, for Moloch and for Chemosh on the Mount of Olives, the only mountain in Israel east of Jerusalem (1 Kings 11:7). The worship, the blessings, and the answers to prayer that people got from their false gods were all a lie.

“that tumult.” The idol worship, the sex and even orgies, and sacrifice that was part of idol worship was just a lot of empty noise to God, just a tumult.