Basically they are rich now because they invested and they are not easily sell for a small hype of bitcoin as you can in the graph or chart of the bitcoin, The bitcoin price is growing since it was created so if you sell in small hype you will just lose the opportunity so I think they have the patience to wait that's why they are rich now.
Not just the patience it takes to be able to hold bitcoin for a long time. But also their belief in bitcoin. They will be patient as they believe that bitcoin prices will reach $ 2500 someday. And that's what brings them rich
I don't think that is belief, I think as a good investor, you really need to stick with it especially when you know that it will be having a good price making your wait worth it. Though waiting for years to reach $2500 is a commendable patience. As we all know it reach $1200 in the past but dumped huge after it. That is so great that they've waited and after that huge dump, because usually they just leave it and change to other altcoin.