The airline with the best safety record in the world, Ryanair, is an all-Boeing 737 fleet (with the exception of the Lauda Airbus A320-200s) that has never had a fatal accident, despite over a 120 Boeing 737 MAX-8s currently operating.
But that RyanAir didn’t happen to have a version of the design that was extremely unsafe doesn’t mean that the family of planes is safer than the competition. It just means that it got lucky that it didn’t have the flawed planes.
That mitigates the risk of buying untested tech with first-iteration demons
That's probably the biggest reason for their safety record: the same plane means common maintenance, training and operations, giving much less risk.