Competition does the exact opposite of centralization. That’s why I can buy most goods from completely different vendors that differ in price and quality.

Competitions have winners, and in this case it means the competition goes out of business and dies, leaving you with a near monopoly or outright monopoly.

That power then gets used to

• lobby (bribe) the government to raise barriers to entry to prevent new competitors
• buy out new competitors
• intentionally price everything lower than competitors, at a loss, to kill competitors in a war of attrition that they can’t possibly outlast

And that’s even assuming there’s any competition at all, which often isn’t the case with certain things like healthcare, internet, electricity, etc.