How quickly the people abandon the difficult ascent for something they can see and touch. Moses is barely gone before they melt their gold into a calf, trading a demanding and invisible ideal for an idol that asks nothing and promises everything. The higher aim requires patience in uncertainty, and patience is exactly what they cannot bear.
An idol is any lesser thing crowned as ultimate, whatever we worship because it is easy rather than because it is highest. The moment the true summit grows too distant, we manufacture a nearer god and bow. People do not fall by choosing evil outright. They fall by grasping the convenient thing when the worthy thing demands more waiting than they will give.