The reality is that they would not have been able to hold for so long even if they bought 10 years ago. Very few have the patience to wait till 100x or more. Most of the investors will be sold at the idea of 2x or 3x itself. Some of the people that were able to hold for so long were those who had invested and then completely forgot about it. There is one more category of people who had complete trust on BTC and thus they stick with it for years.
This just goes to shows that anyone can become a millionaire if they invest wisely. People normally waste their investments by selling it too early and are happy with few X profits when they could literally make much more than that. There are many coins which can still make us millionaire, but we need to invest wisely.