Have you ever thought about Bitcoin becoming centralized someday?
Not the way you imagine, but pause for a moment and think, isn't Bitcoin somewhat centralized even today? I do not mean exclusively where most crypto miners are located (which is difficult to determine precisely), but the fact that several globally positioned crypto exchanges hold several million BTC in their possession. Governments can always reach for a measure to seize all that BTC, for some reason they can invent at any given time.
Of course, the only way governments worldwide will be able to control 51% of Bitcoin's hashrate is if they unanimously agree on using Bitcoin is a "One World Currency". This may all sound crazy, but we cannot ignore it from happening in the future.
As others have already said, it is a little too late for anyone to play with these things, because not only about 90% of the BTC is mined, but in less than 10 years that percentage will reach 99%. In addition, it is inconceivable to me that the US, China, UK, India, or Russia will one day declare a common currency - all these countries are very fierce in defending their national interests, and among those interests is the domestic currency.
The EU has a common currency, but some countries that have been members for a long time do not want to give up their currencies (Sweden, Denmark, Hungary, Poland, the Czech Republic), so even though we are very pro-Bitcoin here, it is more than it is foolish to expect that such a scenario would materialize even in the distant future. I tend to believe that in some 150 to 200 years, money as such will cease to exist - but again, I may be watching too much science fiction (Star Trek)
They can if Chinese government, example takes over all the hashrate from miners in China. I don't think it will happen. They can not do such thing in dark ways and don't let the world know about that. They will slap on their faces by doing this.
But didn’t China ban all crypto miners a few months ago, and most of them left the country? Maybe they just want us to be convinced of it, and at the same time, they are planning a 51% attack?