> But regardless of power, what the NYC mayor does is widely reported and it's often a political stepping stone (if not always successful) to something greater.

The only "greater" things any recent NYC mayors have done are bankrolling presidential campaigns and failed coup attempts.

Looking back at it, the last NYC mayor who held a notable political position after their mayoral term was Robert Wagner.

In fact, the last mayor I can find who served in a superior political office after their mayoralty was John T Hoffman, who was mayor from 1866-1868 and then NY Governor from 1869-1872.