> rideshare drivers are involved in fewer serious accidents than the average person.
Do you have evidence of this? It's certainly true for some kinds of professional drivers (i.e. truck and bus drivers) but I can't find any kind of crashes/100m mile numbers for rideshare drivers.
Anecdotally as both a rider and road user I find rideshare drivers to be some of the worst. Aggressive, distracted, impatient, and overconfident. I would be very surprised to find out they are above average drivers.
Ride share companies use all kinds of techniques to off-board drivers that they deem unsafe. This can be as simple as tracking the driving record and accidents, but they also use the accelerometer in the driver app to assess the location of the car and what G-forces are being placed on it to figure out and predict high-risk (expensive) insurance.
I don't know how aggressive this filtering is, but it is a way to save money on the insurance costs associated with the gap insurance in rideshare. This filter alone would probably put rideshare drivers above average, but that's speculation on my part.
Per mile driven I expect it's true, just given their greater experience than most drivers. Not that I disagree with you that many Uber drivers are not actually great at driving, but neither is the average driver in North America. I expect we just notice rideshare drivers' mistakes more, and get exposed to them at a greater rate.