Why does my window air conditioner cool but not dehumidify?
Don't forget that the percentage humidity is RELATIVE. Cold air cannot contain as much moisture as warm air. For the same amount of water in the air, the relative humidity will increase as the temperature drops. By consulting a psychrometric (humidity) chart, I see your overnight run removed 19 grains of water per pound of dry air. If you rewarmed the morning air back to 81 deg F, the relative humidity would be about 52%. Or, if you cooled the initial air to 72 deg F without removing any moisture, you would get a relative humidity of around 88%. So despite the higher relative humidity reading, moisture was removed.

The moisture removed is a function of the temperature of the evaporator coils in the A/C unit and the volume of air flowing through it. As bib pointed out, the unit may not have been actually running that much, reducing the volume of air passing through the coil, and thus minimizing the dehumidification effect.

If you continue to cool the same air and avoid introducing additional moisture, the humidity level will eventually be reduced. It will take some patience.