the fact is that no one is able to control the price of bitcoin because of its decentralized nature.
No more decentralized if there are Institutional and companies have a lot of bitcoin, like blackrock, or any company like binance who have hundred thousand of bitcoin, they will easy to control bitcoin price on the market in near future, so you have noted it!.
we know gold is very decentralized on past, but after 1 country alot of gold and hoard it, nor more decentralized, the gold price were control who have alot of gold. so are bitcoins, if owned only 1 institution, company and person, I believe bitcoin isn't more decentralized in future, they will control it like fiat, bitcoin will more have inflation like fiat.
While I agree that supply control can be abused for price manipulation, you should still and not mix up the terms inflation and volatility as you seem to have done in your first post.
Inflation within the Bitcoin ecosystem is set in stone for now and deterministic. Everyone can look up the reward schedule and right now we are at 1.7% - 1.8% in newly issued Bitcoin relative to the existing circulating supply.
You are probably referring to purchasing power as Bitcoin is denominated in USD. Of course that varies and has been varying significantly over time. Actually, volatility was what attracted investors, helped the network grow and brought about incentives to improve and grow the global infrastructure for Bitcoin (and cryptocurrencies in general).
Now if you pick specific points in time you can indeed tweak numbers concerning Bitcoin's purchasing power and argue that it performed not very well, but that is very subjective. Nobody in the world would claim that Bitcoin decreased in purchasing power over a 10-year time period. And those who think about it realistically also know that Bitcoin is most likely going to stay highly volatile for an extended period of time. But especially when you take longer periods of time you will see that Bitcoin is much closer to gold than anything else. Gold had its crash of 45% or something from 2011 till 2016. That is why an investment like Bitcoin shouldn't be understood as a short-term gamble. You can be lucky and catch a fantastic bull run momentum, but it can also end in a catastrophe if you need the money in a few months from now and are forced to liquidate your position.
Again, inflation for Bitcoin, in contrast to fiat money, is set in stone as per the parameters hard-coded into the protocol. No single centralized entity has a printer in their basement and can freely issue some new Bitcoin.
From where we are now Bitcoin still has a lot to gain, not least in terms of general acceptance among people. That is different for all the well established fiat moneys. The USD doesn't need to be accepted anymore in the sense that people need to familiarize themselves with and understand its mechanics better (although they probably should). The USD can crash for inflation reasons when new USD simply get printed and it can crash for economic fundamentals when the economy backing it underperforms.
With Bitcoin there are less uncertainties in my opinion when it comes to shenanigans that a government can apply out of the blue and to be honest, not so many people do actually follow the numbers like circulating money supply when it comes to fiat money. The average Joe just notices that there is less food for more money in his basket at the end of the day.