How could Moses ask Almighty God for a vision, despite the warning of the "thunderbolt" that struck the Children of Israel when they made the same request? And was his request a way of silencing his people, as Abraham did?

Moses (peace be upon him) requested to see his Lord because it was possible, and Allah did not rebuke his request. Rather, He made the vision contingent upon the mountain remaining firm. This indicates the possibility of seeing Him in this world and the Hereafter. Allah negated comprehensive perception of Himself, not vision. As for the Children of Israel, the thunderbolt struck them because they made their faith contingent upon seeing Allah openly, not merely for requesting the vision. Moses' request preceded theirs and was not intended to establish a proof against them.