Answer is already on your post. Banks can’t give you an interest greater than 5% while this crypto exchange which you didn’t know physically located or have claim whenever they run offer a lucrative percentage. DeFi on crypto is pure gambling despite they are promising safe passive profit because exchange has a chance to runaway or got robbed including your money.

Why not just hold Bitcoin and wait until the next bullrun. You can earn more than 15% safely if you will never sell at loss.