I agree with you that we have become afraid of a scenario that has become very likely, which is that Bitcoin will become a tool of control, despite its decentralized structure. A limited number of Bitcoin units makes it a scarce value, and everyone will seek to own it. With the expansion of individual ownership, Bitcoin will become a store of value, and those who own the most will be able to control the supply and demand market. A decentralized design does not mean decentralized use either.
I wouldn't say that they are going to control the supply and demand market, as this is close to manipulation. And we have heard this before, that a large whale could manipulate the market but we haven't seen any proof yet.
So as far as entities goes, it's the exchanges, casinos, and personalities like Michael Saylor who might have a huge bag but it doesn't mean that they have total control. For me it is still us average joe investor that makes up the most of it as some of us could be in the market for so long already.
Currently, there are no whales on the scene capable of manipulating the market, including the reserves of countries or even major platforms. However, let's not forget that the trend toward greater adoption of Bitcoin will encourage whales of all kinds to feed their wallets, raising the possibility of potentially waking up one day to find the United States or China, for example, pursuing a plan to acquire significant portions of total bitcoin supply, directly or indirectly.