Many people make more money in a year trading crypto than others earn in a lifetime of wages, so why bother working a regular job? Many people get 100% annualized returns from DeFi mining, surpassing 25 years of bank financial products, so why save in a bank? Many people might say: This... isn’t stable, right?

Yes, it’s unstable, a very good question. A year surpassing a lifetime—why does it need to be stable? It doesn’t need stability.  
The real key to the issue is why you would even ask the question “Is it stable or not?”