Another question: how can they even "cash out" from the legal standpoint? Surely tax authorities will be interested in those millions of dollars "out of nowhere

Another question: how can they even "cash out" from the legal standpoint? Surely tax authorities will be interested in those millions of dollars "out of nowhere". It's possible to "stay under the radar" with small sums (e.g. buying your groceries with "BTC credit card"), but surely not with millions, right?