I'm not one of these people or know any of them, so you might very well be right.
In general, though, there are usually a (small) number of people observing any field who should be doing professional analysis work, but who don't "think they could do that sort of thing" or think it "takes someone way smarter than them." They have too low an opinion of their own knowledge to think it has value. So, instead, they go on giving away extremely high-value market analysis for free in the comments section of some blog.
As one example, we can look at the forecast Burry is best known for, from The Big Short (and the corollary film depiction), and I found myself identifying much more with Michael Burry's investors than those who praised him at the end of the story. Scion Capital was hemorrhaging its investors' money, and for a nontrivial amount of time even after it became widespread knowledge among the institutional elite, the market failed to crash and vindicate Burry's short. From Burry's perspective, everyone around him thought he was wrong, but this misses a lot of the nuance. His fund's investors weren't necessarily concerned with him being right or wrong per se, they were concerned with the ridiculously inane risk he decided to take with the entirety of the firm's capital. It's great that his bet turned out so well for him, but calling it genius (as many do) is so charitable as to be almost literally incredible. Michael Burry could have easily been right but unlucky, and simply run out of capital before he could make a return on the short. This is why the saying, "The market can stay irrational longer than you can stay solvent" is so important.
Look at this from the perspective of Burry's investors, not the retrospective story of Burry's victory. If you were an investor in a hedge fund, and one day out of the blue the CEO emailed to inform you that the entirety of the fund's capital would be liquified to leverage a single market position, and that you would not be allowed to withdraw any of your capital, would you react with approval, lukewarm disinterest or abject horror? Even if you bought fully into Burry and his strategy, would you have the requisite nerve to be comfortable with such an astronomically risky and contrarian position?
That said, one of the things that impressed me most about Burry is that he could withstand such intense and prolonged pressure from both investors (harassing, suing and ostracizing him) and significant financial loss (albeit ultimately unrealized). It takes incredible fortitude to be able to lose that much capital in the pursuit of a positive return.
People can make correct predictions, but there are tons of nuances around them. You could have predicted the Note 7 disaster, but Samsung's stock is up 27% from its pre-incident price. Maybe you knew about VW's problems years ago. Oh, too bad, their stock is up over 50% since 2011. Oh, you knew about the Toyota mat problems? That entire incident amounted to a nearly invisible blip on the stock price.
Betting nearly a billion dollars of other peoples' money on one single thing is absolutely insane. There are a million ways to be completely right and still lose everything.
Not disagreeing with your points about the million ways you can be right (and be unable to execute on it), though. Just that there are about a billion ways to be wrong, and a lot of those come from not taking a broad enough perspective about the impact. Burry did the research, saw the systemic complexity and dominoes that would fall, which perhaps gave him a little more confidence than a CNBC blowhard just looking at some new high in home buying and calling a market top. But he absolutely could have been wrong if he executed poorly.
This is a good hypothesis, but it is far from obvious.
I remember, years ago, unwinding a portfolio of correlation trades. The trades consisted of bets on how assets would correlate, e.g. Apple might be expected to correlate with Microsoft more than with Société Générale, a French bank. We were under a time crunch to unwind the massive portfolio. Given the structure of the trades, unwinding them meant reversing their implied correlations. Thus, for one week, the market's largest names anti-correlated with reference to how a few traders had previously thought they should have correlated. The moves were noticeable; the attribution far from obvious. Nevertheless, talking heads proceeded to breathlessly blame political crises in Spain.
To properly attribute this Bitcoin activity to the People's Bank of China, one would want to examine country-level Bitcoin flows of funds around the time of the PBoC announcement, paying attention to hourly data around when the Chinese- and English-language announcements were made/leaked.
These moves are mostly retrenchment and speculative/sentimental response to China messaging though. Consider -- if there was real, imminent concern that Chinese exchanges might be shut down and funds frozen, would the price at these exchanges fall or rise?
It would rise, because getting BTC out is going to be far safer than fiat.