Bitcoin price is also not stable.
What can you expect with a coin that's decentralized and isn't controlled by the government?
Crypto isn't stable because there aren't enough people in it, it's that simple.
You just can't compare the amount of people trading BTC vs the amount trading EUR or USD.
And BTC, still being at the top, is still the most stable crypto (which, again, does not mean stable, at all). Those who are saying that ALTs are more stable, are probably very new.
There's also the fact that the distribution of coins is just flat out terrible. In BTC, you have people like Roger Sperg or the Winklevii who control enough to move the markets by themselves, not to mention what would happen if Satoshi came back and decided that dumping would be entertaining. Plus the fact that anyone can hold multiple wallets, so for all we know, there's some secret mega-whale out there that has even more than even those people. Of course this isn't unique to BTC. There are other cryptos that are even worse. It's not unusual anymore for the devs of whichever shitcoin to reserve the majority of coins for "future plans". Until, or maybe I should say unless the distribution is more evened out, it's impossible for crypto to be stable. There's just way too much power in way too few hands.