Decentralized systems often settle into some kind of "power law distribution."
For some reason some people think decentralized means a socialist network where every node is exactly equal. That is never going to happen.
Look at gold production as a analogy.
Lot of people buy/use gold but only a tiny fraction actual mine gold.
Someday lots of people will buy/use Bitcoin but only a tiny fraction will actual mine coins.
Gold mining is decentralized with operations around the globe.
Bitcoin mining is decentralized with operations around the globe.
Although no company has control of Gold wholesale market roughly a dozen companies produce the lions share of the world's gold.
Although no pool has control of Bitcoin supply roughly a dozen pools produce the lions share of the world's coins.