“lay his hand on.” This is an idiom meaning “to harm.” God did not harm these leaders even though they saw him.
“they saw God.” The Hebrew word “saw” is the verb chazah (#02372 חָזָה), to see, but often to perceive, to see with the mental eye. When contrasted with Exodus 24:11, chazah means more to mentally perceive. The leaders of Israel saw Yahweh with their eyes (Exod. 24:10) and understood what they saw (Exod. 24:11).