Also, shortages of small cars from the car companies may get in the way of rental car companies shifting their fleet mixes (retooling factories from trucks and SUVs to small cars without advance planning is not instantaneous), just as retail buyers are finding new car dealers filled with unwanted SUVs but sold out of small cars.
That was my thought as well. Mfrs can't sell their SUVs, so they'll probably drop the price for some rental agency to buy them...and the rental agency will have to keep trying to convince consumers that this is an upgrade.
Eventually, when the manufacturers catch up and stop making so many gas guzzlers, things will probably even out. My guess is this will take a few years....