Bitcoin is free and it's not controlled by a party. But ripple has already fully controlled by the company. You may need to read more about how both of these platforms works. I hope that you can try to see the fact if bitcoin is fully decentralized.
In our world, nothing can be completely decentralized, even Bitcoin. I think that many influential people have already bought more than 30% of all bitcoin. Ordinary people have very little Bitcoin.
Bitcoin is decentralized in term of its system, stellar is centralized in term of its system.
But in the market, Both can be controlled by whales, this is money power
we can't blame that, people who have much money indeed can do as they want.