The same happened to me. I bought a bit of doge years ago with no intention of my buy being a trade or investment to make profit. I originally was just trying to figure out how this all worked. I totally forgot about it until recently.

However, I'm assuming this guy put down a significantly greater amount of cash down than either of us did. He couldn't have made millions by a small amount bought. I assume he had some insights by analyzing the technicals of the price movement. Based on his background, that assumption seems reasonable. Otherwise, he was willing to buy very early on and risk say $10k on a cryptocurrency that doesn't really have any valuable fundamentals... besides that it's a meme and it's funny that you can make fake money out of meme. People bet more than that on horses in races with no rational basis or he has lots of disposable income, so it is possible he made the trade on a whim.