Wow, Amazon seems to want to help publishers to kill off retail products. Their behavior over the last few months has been pretty annoying. Though it's not always clear who's the one to blame, Amazon or the publishers.
You are making a lot of assumptions. If I had to guess, Amazon didn't want to cancel anyone's preorder. My guess is they canceled it because either the publisher decided to stop selling games to Amazon or there is a business disputer between the publisher and Amazon.
One thing to keep in mind is Amazon used to have very low video game prices. That cannot have made publishers happy because Amazon sold a physical copy for less than a digital copy. Publishers and console makers didn't like this for the following reasons:
1) They made more money off of digital sales.
2) Digital copies cannot be resold.
So, Amazon was encouraging people to buy a version of the game which made them less money and could be resold. How happy do you think that made the console makers and the publishers?
My guess is the continuing supply issues you are seeing at Amazon (including weird pre-order issues, Amazon not selling Nintendo consoles itself, etc.) are related to Amazon's disputes with various video game industry entities. Amazon wants to pay the same wholesale prices as everyone else and then undercut companies like Gamestop, BestBuy, Walmart, etc. They console makers and publishers do not want Amazon doing this because it undercuts their own online stores and angers their other retail partners.
I could be wrong but I suspect I am at least partially right. I bet this is really about money and if I had to guess, part of the dispute is about Amazon charging "too little".