Introducing gradually to the journey of a coin is the right promotion step, Bitcoin takes the step to find the right format, so that today we can see how strong this coin survives in the market. Unlike Altcoin, they only pursue votality and temporary strength, but in the long run they cannot maintain, there are only two that are still strong for now, Ethereum with BNB
Bitcoin does not need any promotion, it get promoted on its own. 
The popularity of one coin does not lead to a bad outcome even when its price fluctuates, like I said the yearly volatility remains within controlled limits.
Though altcoins also see pump and dump they too remain close to this when seen on a long term scale like a year or a half. Specific altcoins might be doing better on their creators promotions, still bitcoin remains the big one.
Price remains stable in the long run, if you know how to take advantage of it. Besides without the price changes we would not have any trading happening.