It is important to realize the effects that this consolidation has in terms of wage stagnation [1]. This is a very real effect that is felt by a very large percentage of the workforce. By consolidating wealth (and power) in the hands of few large companies those companies are able to pay a lot lower salaries to their employees. If your options are (1) work for Walmart for a low wage, (2) work for Amazon for a low wage, or (3) starve, you will accept whatever wage Amazon or Walmart will offer you.
In other words, as a direct consequence of these multinationals and their mode of operation, millions of people are getting lower salaries today than they would have gotten 50 years ago (adjusted for inflation) whereas overall productivity has gone up significantly. The difference is pocketed by executives and wealthy shareholders of these companies. As a result of those lower salaries, those people are now having trouble paying for core necessities (health care, education, housing).
This is the rising wealth inequality that people are talking about, and the rising wealth inequality that people want to fix.
[1] https://insight.kellogg.northwestern.edu/article/wage-stagna...
I get where you're going with this... and I'm not in favor of monopolies and anti-competitive behavior... but Amazon is a hugely innovative company, and I do not believe that they've merely consolidated wealth without creating any. Think of just AWS as an example and all of the companies (and their employees) who've created more wealth as a result of it.