Re: Fault tree
At the FAA it's a combination of regulatory capture after Congress continually cut funding. As a result the FAA didn't have the resources to do certification testing, so it let the plane makers self-certify.
And, as much as I agree that it should take as long as it takes to solve the problem, Boeing and Airbus, and for that matter Bombardier and Embraer, have incredible safety records. But the 737 Max was attempt to bend the results to speed up time to market and charge of criminal negligence shouldn't be ruled out.