Bitcoin's volatility will never be controlled, just look at other commodities like gold and see the big swings that happen there. Even fiat currencies often have large swings in their valuation.
"Big swings" is relative. Neither gold, silver, or other mainstream commodities, and especially not fiat, see volatility on the order that crypto has experienced in its short lifetime. Gold on rare occasions can swing 10% in a day, and that's a big move. Crypto routinely swings 20% or more in a day. Fiat is generally more stable than gold, and a few percent in a single day is a dramatic move. (Fiat during hyperinflation is another matter, it's not common and not normal, and is generally a one-way track.)
Which perfectly cuts it as a mainstream one and which has volatility quite on par with that of Bitcoin. I obviously refer to crude oil which you kinda forget to mention. I guess it is as mainstream as mainstream itself is concerned, and it is not uncommon to see huge swings in the price of this commodity within a couple of days (up to a few dozen percentages). And it is not just about short-term volatility either. Long-term volatility of crude oil is also quite remarkable. But you certainly know that even better than myself