This day length corresponds to the semidiurnal resonant period of the thermally driven atmospheric tide; at this day length, the decelerative lunar torque could have been canceled by an accelerative torque from the atmospheric tide, resulting in no net torque and a constant rotational period. This stabilizing effect could have been broken by a sudden change in global temperature.
The duration of this day aligns with the semidiurnal resonant period of the thermally driven atmospheric tide; under these conditions, the lunar braking force would be counteracted by an atmospheric acceleration force, leading to no net torque and a stable rotational period. However, this equilibrium could be shattered by a sudden shift in global temperature.