The ports only care about inbound cargo, not outbound empties. So they have no incentive to have enough space for empties. The surge demand has suddenly deplet

The ports only care about inbound cargo, not outbound empties. So they have no incentive to have enough space for empties. The surge demand has suddenly depleted the free spots is removed until its a trickle. Then you get this result. The ships are stuck because the ports had no incentive to reserve space for empties. Or, something like bufferbloat.