There is also the angle of: even if there is an appropriate amount of controllers in the tower at a given time, how they do it can also hint at the issue. Being an ATC is a taxing job, mandatory overtime and 60 hours work weeks screams understaffing to me.

It is possible for ATC to be understaffed as a profession, LGA to be understaffed as an airport, individual controllers to be overworked, and for it to be 100% reasonable to have a single controller at LGA in the middle of the night.

Its weird that there strict laws that limit pilot hours to under 40 hours a week but no laws that restrict number of hours ATC works.