That does not has to be like that, every crypto may be stable if the volume is high, and the traders do not create big gap between sell orders and buy orders, but that is only in case if the disagreement on the value of the crypto is not different so much.
You are saying that the bitcoin has a stable growth, but there has happened a lot of collapses. You should always remember that every single chart, no matter of what asset looks like that. It is not possible to see the price constantly growing, every single financial instrument price needs to drop at least some, to increase its price even futher.