I am sure, aside from accumulating Bitcoin, he is also diversifying into other investments and business ventures. It is common for smart businessmen to have 2 or more investments or business ventures to ensure that their financial flows to earn more is well established.
About Bitcoin, as long as it keeps on uptrending, no matter how it fluctuates, it will always be the most dependable asset and investment.
When you do make a lot of money, investing by diversifying is great. But for me, I always side with the person who reinvests back into his job, there is no limit unless you are Elon Musk, you can always reinvest and go bigger, even he can.
The best thing we are seeing right now is all those rich people actually believed in themselves and took a risk and that's how they became big entrepreneurs and wealthy people. Of course it comes with a risk, you may lose it all as well, so having a side investment would prevent that, but I rather take that risk. For becoming a millionaire, lots of strategic works needed and being prepared for risk taking would be the very first step toward that.