The local spot prices dropped below zero. The price of gold might be 1000 currency units an ounce, but if my house is about to collapse under the weight of all my gold I might pay you a little to take it off my hands - dropping the price below zero for the people in my immediate vicinity.
Spot prices can be very volatile and easily drop below zero. If your stores are full and you have nowhere to put gas that might be building up inside an incoming pipeline, you'll be happy to give it away for free. But once it gets cold and people start using more gas, you might pay those $2B for the gas in the tankers off your coast to satisfy increased demand.
Depends on where those ships can offload the LNG. If they were in Asia or the US Northeast, prices would not be negative. (But prices differ by significant multiples between those locations)
The $2 Bln quote could be historical but in real time live spot prices at the present, the rates cratered momentarily to zero or even negative territories.
Luckily, LNG ships can simply be parked at sea until prices rise again, same for oil tankers. Pipelines going into almost full storage don't have that luxury.
It costs money every day to leave the ships parked and idle, but in some ways it is a good thing. Those ships are basically extra storage in the event of a long cold winter that stresses the natural gas supply harder than expected. They offer flexibility to deal with pipeline shortages.
The costs of having those tankers parked is orders of magnitude less then the value of their cargo and potential profits.