China was the only country working full speed after the Wuhan lockdown for about a year. The entire world bought masses of PPG and ventilators in addition to our normal plastic consumerism widgets. China sent tons of full containers to the rest of the world but those containers haven’t returned to China.
Everything else is a symptom of some local issue due to a region or industry being host to a disease outbreak or being host to a supply/demand mismatch with either containers or chassis.
Even that distribution lot would not need containers stacked above 2 high if the distribution channels downstream of it were not similarly overloaded.