Simple, they borrow your money for ~8% and they lend it out for ~11.9% (no loyalty, this used to be 24.9% but I guess they changed it because it made them look like loan-sharks).
The concept behind Nexo is to make Crypto as liquid as possible for clients. Instead of selling crypto you can temporarily supplement it for a small loan.
Their average loan is well above the 5.9% minimum and more people are using the service to borrow rather than lend.
They are profitable, but don’t expect the stablecoin interest to remain at 8%-12% long term, it’s to attract new customers! Just like Crypto.com did.
One thing to note, the business model is SOLID, but only in a stable or bullish market. If for some reason Crypto market tanks, then it could become an issue.