Saw the thunderings, i.e. heard them. One sense is oft put for another, as seeing, Genesis 42:1, for hearing, Acts 7:12. They removed from the bottom of the mountain, where it seems they stood.
Related Commentaries of Exodus 20:18
Exodus 20:18
18 And all the people saw the thunderings, and the lightnings, and the noise of the trumpet, and the mountain smoking: and when the people saw it, they removed, and stood afar off.