Only 7%? At the height of the bubble, there were a number of major crypto schemes offering interest rates of 20% or more. Sometimes even much more; some of the shadier "investments" offered >100% APY.
Unsurprisingly, most of those schemes have since collapsed.
It’s easy to give 100% APR in a token you’ve created, it’s very hard to keep the market value increasing at a similar rate to offset coin price dropping. Initial hype will support you for a few months but it’s all tears in the end :)
I’m still sort of sad the focus hasn’t been on decent remittance systems, the true useful tool of crypto IMO.
Or even simpler: if you put barriers in the way of users cashing out their "earnings", you can keep a naked pyramid scheme running for quite a while. Some schemes have done this by making it difficult for users to cash out their earnings, e.g. by enforcing a lockup period, or requiring users to sell their tokens to another new investor, or even by simply declaring that withdrawals are a feature "under development".
Unsurprisingly, most of those schemes have since collapsed.