Moving from the era of Real estate to stocks to metals to oil blocks and now digital assets we would agree those who made it big in all this investment options were those who had the patience to hold.
From the history only ponzis are profitable in short holding and all other real potential based opportunities are proven to provide big returns in long term holding hence digital assets cannot be an exception here. If you find any opportunity is profitable in long run then that must be categorized as legit and at the same time if short time profiting opportunities which are providing realistic returns like 2% to 10% then that also might be legit.
Short holding may not be profitable in fair stuff, but day trading could be. Imagine a person who puts up 1000 dollars on a 100x leverage and opens a long, and the price goes up 10% the very same hour he does that, sounds unlikely I know but definitely possible. This is how you make a lot of money in a very short amount of time without it being a scam.
Now, would I suggest doing that? Of course not, you are going to lose 90% of the time and that 10% of the time doesn't really worth it and instead of losing "some" of your investment like spot trading, you are going to lose it all so it definitely doesn't worth it at all. I just wanted to show you that it is "possible", although it is definitely not worthy to take that risk.