[linhns]

I believe this is due to the USPS loophole being closed, tariffs only play a small part.

[sowbug]

It may also have been because of the end of the de minimis ($800) tariff exemption. Without that exemption, even something valued at one cent would have to go through the import-tax collection process, which meant that small packages were no longer economical to send. That exemption is still gone.