No wealth was created or destroyed in the making of these millions, the millions simply changed hands. Think about that before purchasing a cryptocurrency. You're basically handing your money to an earlier "investor" in the hopes that a future "investor" will hand a greater amount to you. This is all there is to it.
Isn't that the case for pretty much all exchanges? How is that different than in the stock market?
In case of a sustained growth of a company (think Apple over the past 20 years) what the shareholders gain comes from the earnings of the company. Apple shareholders have gained trillions in the past years - no one has lost an equivalent amount.