The article pointed out that some airports don’t have the electrical infrastructure to support enough super chargers. It’s partly a charging problem

No one said "supercharger."

If I can get a Level 2 charger installed at my house, surely it can be installed at at car rental business?

No way my house has better electrical infrastructure than an airport.

2 hours is still a lot longer than 5 minutes. Rapid turnover is important for these folks. I've seen rental companies run out of cars numerous times. Two hours is tough. Plus, how about when dozens of cars have been turned in and are waiting on a charge? If anything, they are most likely to levy a higher fee for returning uncharged because of their lost time.

you still have to clean and process ready for next customer. adding 2 hours to other work may make it half a day

You can't clean the car while it's plugged in?

It would seem ideal to have the line-up area where cars are turned in, inspected and cleaned set up with a bunch of retractable charger leads in the ceiling, ala shop air. As soon as you pull up, the attendant pulls down a lead and plugs the car in. Bam.