I think this has much more to do with the fact that people drive cars and not airplanes. Most people have confidence in themselves and not others (cf. George Carlin's joke: "Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?"). So they're happy to make things safer if those changes only affect other people (as in an airplane). But when it comes to the fixes that would do the most to reduce traffic fatalities (e.g., lower speed limits on non-highways, more speed cameras, or perhaps most pertinently technology in cars that would make it more difficult to speed, etc.), those affect you too.

If the MAX had continued to fly without getting to the root cause it would have been a completely different story than the one that we have today, which is bad enough as it is with both Boeing and the FAA owning what they broke.

Because road traffic deaths are rarely in the hundreds range per event due to preventable criminal negligence. When a bridge collapses and tens of people die, nobody tolerates it.

You’re making a misleading comparison.

If you want to liken the 737 MAX’s failures to road traffic, you have to ask yourself if there’d be broad acceptance of shoddily built, fault-intolerant bridges and freeways. Moreover, would that acceptance be greater or lesser if the public knew that engineers believed their designs were flawed?