Just a speculation, if it's true that Elon made billions on DogeCoin pump, he could have reported taxes on what he earned, you know he is a influential person, he should be more compliant on the law, otherwise it will affect his business reputation which is also billions of worth, and since we didn't here any news about that, so there's no valid proof here but a mere speculation.
True, but taxes need to be reported and paid only on realized gains - if you invest in crypto and it appreciates in value, you don't need to report it on your taxes until you sell it for fiat. And, there is no requirement that Musk (or anyone else) make their tax returns public - see the debate around Trump's tax returns. Even very prominent people aren't legally required to release their taxes to the public. Musk doesn't release his taxes, so there's nothing to report on. There's no law that says "your taxes are private except if you're rich". Everyone has the same legal right to tax privacy (even if we might believe in some moral or public-interest sense that the very-wealthy ought to be excluded from such protections).