Really easy way to suddenly introduce millions of dollars in a suitcase and say, "oh, I just sold all my bitcoin on some marketplace somewhere, thank you very much".
Your post is the most correct. Bull's-eye! In Ukraine, there was a case when a parliamentarian announced that he had won his millions in the lottery. And he won the jackpot several times in a row - "lucky". In Ukraine, officials know how to launder money stolen from the state.
Where I come from, we are the same, politicians cut from the same cloth. My country's own prime minister (ex now) famously made global headlines with billions of dollars stolen from national funds. Big enough when viewed from USD perspective, unimaginable to most people when converted to national currency. His explanation was even easier: he receives unsolicited donations from other countries who just love his policies. Donations!
Waiting for some minister one day to say he bought Bitcoin from Satoshi.