Earning 10% "riskfree" isn't speculation, it's a Ponzi. What serious borrower needs to pay 10% to access credit? So then, who are the borrowers who are paying this interest? As they say on Reddit: !remindme 1 year.
People who can make more than 10% trading?
Lending protocols aren't doing anything different than what banks do: allocating inactive capital to those who can make use of that capital and are willing to pay for it.
Interest rates are high because of A: market volatility, professional traders can easily make more than 10%, and B: information asymmetry, large capital pools haven't allocated to these pools.
Lookup what a ponzi scheme is.