Genuine question: How is it not centralization in consensus if a few staking pools end up being the majority?

See thread here from SparkPool.eth

https://twitter.com/sparkpool_eth/status/1395662646951641090

If you add Coinbase, it will likely take us past 51%, doesn't it mean all those names listed (except for whales/DeFi) will be able to control the network?

Please help this noob out. Seems like such an obvious question they have thought about already, can't imagine there isn't some game theorical mechanicms they have designed against this??