When they were but very lately brought out of Egypt by such wonderful power and goodness of God, and had seen the dreadful plagues of God upon the Egyptian idolaters, and upon their idols too, as is noted, Numbers 33:4, and when the law of God was but newly delivered to them in such a solemn and tremendous manner, and the most high God was yet present, and delivering further precepts to Moses for their benefit upon the top of that very mount. This greatly aggravated their sin.
Related Commentaries of Psalms 106:19
Psalms 106:19
19 They made a calf in Horeb, and worshipped the molten image.