only stupid people do all in, they believe too much that everything will go according to what they want? whereas in the market prices can go up and down, and that is a sure risk of a crypto market. if the price falls, of course it is an opportunity for investors who still keep money (backup funds), you dont should use all your money at once dude!
Still depend on what that "all in" meant. It is stupid when it meant that you're fully diving yourself along with your assets in crypto. Why would anyone do that in the first place? Profit could multiply in an unimaginable numbers, but nobody got that kind of guts to even risk their land for that kind of gambling. All in could also mean that they're committing their capital fully in the market. Like from the numbers of coins existing in the market, they're committing it into one, which I think is in Bitcoin (as what the OP seems to point out). It's nothing different to going all in at poker, you lose, you win or it is gonna call splits.
of course no one has the courage to use all their wealth. as the OP said that he only uses all his investment capital for bitcoin. and in my opinion it's not a good idea. whatever the choice of investment, using all your capital for just one asset is not a good thing. you have to split your capital into several other assets and don't forget to backup funds