Question about staking yields.

So I'm looking a lot into staking and notice that staking ADA is most popular, with around a 3-3.5% yield currently. How do yields work when talking about cryptos such as ATOM that's offering a staggering 20% yield, which seems too good to be true and if it really worked like that why isn't everyone doing it? I've seen a lot of comment saying to adjust for inflation but how does that actually work? 20% seems ludacris, there's obviously something I'm not understanding, give it to me in simple terms.