That wasn’t based on lobbying, it was the law at first and Amazon took advantage of it.
Amazon didn’t have any significant lobbying 20 years ago and it definitely was the behemoth it is today. That being said, even today it isn’t as large as Walmart and was definitely not a large retailer back then.
It was seriously in doubt 20 years ago whether Amazon would ever survive and definitely wasn’t consistently profitable.
Totally, I completely agree that they didn't lobby for the original exemption.
However, I would be very surprised if they weren't lobbying heavily to keep said exemption for as long as possible.