All retailers have to go bankrupt for amazon to earn enough money to support the stock price. That means unemployment atleast tripples, and people have no money to buy junk from anywhere. The political pressure that brings and taxation will take care of everything else. So it is morally important that traditional retail survive and online retailers have to compete on fair terms. Once the tax advantage is gone, shipping separately same day to everybody's home, or shipping to a store once and everybody picking up from the store will have no cost difference including store maintainance.
People will always pay a little more to go try and buy it from a shop and get the support anyday.
The retailers will force major brands to sign exclusive deals so that they can't sell with online only retailers. Those brands with support from store and online combo will have their products displayed, tried out and sold for a profit.
Junk staying with online only will face returns galore and loose out. People will get tired of returning unfit junk to online only stores and the sales will #$%$ out. Finally before the death spiral of online only retailers who don't make profit, they will try to buy struggling retailers to have a store front. Ultimately things will be back to normal and the story will continue. The exhorbitant PE will go down the tube and normal expectations begin to settle in. And share prices will return to double or single digits based on profitability.