Years ago when Teslas still qualified for the original federal EV tax credits, Tesla would add the tax credit to the residual value. For example, if a car had a residual of $50,000 and a tax credit of $7,500, the residual would become $57,500. This helped lower the monthly payment but also made the car $7,500 more expensive to buy at lease end. Lessees who chose to buy the car essentially had to pay for the tax credit. I think this was Tesla's way of discouraging people to buy at lease end. You can't even buy new Teslas at lease end right now.
As far was what Telsa is doing this year, it may be a combination of things including lower rates, lower cap cost, higher residual, etc.