Low volatility doesn't mean stable. Bitcoin has experienced periods of low volatility many times, however this doesn't mean bitcoin is stable, not even close. We all know it doesn't take much for bitcoin to explode, either up or down. That's absolutely still in the cards, I mean everyone is waiting for the next bull run and some people are waiting for a big crash.
It's like saying, this bomb is stable because it hasn't exploded yet.
Yes, the bitcoin price is like the other altcoins, volatile in the market. But i think bitcoin is more stable than altcoin price.
Few months ago when altcoins going down with significant difference, btc price is only going down for few percentage.
But yes, all of the cryptocurrency price is unstable in the market, often to fluctuates.