ACTUALLY, PRETTY MUCH ANY COMPANY YOU BUY THINGS FROM IS NOT YOUR FRIEND
FRIENDS BRING PIZZA
There is a big difference in this case.
Normally, a producer of something (hardware) is providing a component in the value chain. They try and make a better product so you will buy it over their competitors alternatives.
In this case, Bitmain is mining themselves and they are your direct competitor. They have economic interest in destroying your economy and pushing you out of the "market". They are doing this on the grandest of scales and it's actually happening just in front of us. For a healthy market to work, there have to be more than one manufacturer (eg. Intel, AMD, Nvidia). Also, the manufacturers can not be your competitors.
As a thought experiment: Extrapolate what would happen if Intel, AMD and Nvidia took their respective resources and went all in on POW mining. Others could only buy yesteryears hardware in the shops when these companies sought fit. You could extend this for all forms of professional computing for that matter (not just stupid mining). Would there be any market for long ? Who would be in power of those blockchain projects after a while ? Who is in power of these companies? How would that affect the philosophy of crypto to liberate us from central control over everything ?