I don't understand whats the problem with that?
According to Amazon they found it difficult to workout what was and wasn't an essential item according to the rules. I would imagine with a catalog as big amazon that's probably true. They decided to shutdown instead which is perfectly rational given the amount fines placed upon them if they did accidentally ship an item. The goverment got what they requested, no non essential items shipped.
I would imagine amazon would have preferred to keep operating, so I believe them.