One way Amazon was able to compete on price was by not having nexus in most of the country. Consequently, Amazon didn't collect sales tax on behalf of states and consumers, on the whole, never declare use tax. I still see that mentioned on most deal-hunter sites: "tax kills the deal" or "order from X and you don't have to pay tax." It's tax-free in the same sense that all tax evasion is tax-free. But, sales tax is levied at the state level and states don't have the resources to audit everyone.
That's not to say that Amazon didn't execute well. And their selection was excellent. It's just really easy to compete on price when your checkout total is 5+% cheaper than an in-state competitor even when the items were priced the same. Of course, this only applies to states that levy a sales tax, but that's still a large portion of the US.
I've read your comment a few times and I can't really tell if you're trying to refute what I said or if you're agreeing with it. I don't think mail order operations ever amounted to more than a tiny fraction of what online purchases are today. They were certainly nowhere near as convenient.
Setting that aside, my point was Amazon had a built-in price advantage that brick & mortar retailers did not. Use tax really should have been the normalizing force there, but no one declares it and it's hard to enforce. So, all things being equal, consumers would shop where they could realize a price savings. The story of brick & mortar retailers transitioning to e-commerce is more nuanced than some titan resistant to change being taken out at the knees by some peppy up and comer. Amazon was quite aware of this and fought very hard against any change in rules regarding collection of sales tax.
That's not to say that Amazon didn't execute well. And their selection was excellent. It's just really easy to compete on price when your checkout total is 5+% cheaper than an in-state competitor even when the items were priced the same. Of course, this only applies to states that levy a sales tax, but that's still a large portion of the US.