BTC has more than doubled several times in the last decade. GME and AMC (and many others) doubled and then some over a few days. If you take reasonable gambles with known risks, doubling your money is not that hard to do.
Rightly said but let's consider an example. You know if you bet on Djokovic to win in 4 sets against Zverev you would have doubled or even tripled your money, so did you miss out on that? That is how you are talking because yes one could have doubled their money if they invested in right coins at the right time and the right amount, which is not easy to actually do when you don't know how the market will behave in future.
Also have you actually doubled your money then? I don't have a crystal ball with me that can help me determine the prices of altcoins or bitcoins in future, if you have one please share with me man. And hey no hard feelings, I was just trying to tell you how hard it is to actually double your money and how easy it is to advice someone to double their money.