I can't agree with your statement because long-term investment in Bitcoin is not the only way to get profit. A lot of profit can be earned even by short term investment. Many times it is seen that many people invest in Bitcoin for a short period of time and earn a lot of profit. If you have a large amount of bitcoins you will be able to earn a lot of profit from bitcoins even with short term investments. Let me show you an example how to earn profit by investing large amount of Bitcoin in short term.
just as @FinePoine0 said that no investment, is just like trading. You can't actually compare that to long-term investment profit. What about in scenario, market did not go your way when you invested that bitcoin for short-term profits . Due to fact that your are in a urge of making quick profit you may endup selling your bitcoin in loss . And when you are exercising long-term investment, it would give more chances to stash more bitcoin In your portfolio. (Like time range of 5-10 years holding even more than) of accumulating. Holding for long-term Is more safer than short-term, though bitcoin may undergo some dip and all that, during it growth. But still bitcoin would keep on growing so as your portfolio as an long-term investor.