I think the idea is that the people lending are planning to hold onto those stocks over a long period of time, so they are hoping that in the long run the stock

I think the idea is that the people lending are planning to hold onto those stocks over a long period of time, so they are hoping that in the long run the stock price goes up. While they are holding onto them, money can be made by lending out the stock. The security lender will lend stock, get a fee for doing so, and will hedge against risk by getting collateral for the stock they lend.