Clementine Cheetham:
I suggest you read the following for some insight on how these kinds of things happen. It's not an isolated incident.
https://science.ksc.nasa.gov/shuttle...-contents.html
From Chapter 6:
2. Prior to the accident, neither NASA nor Thiokol fully understood
the mechanism by which the joint sealing action took place.
3. NASA and Thiokol accepted escalating risk apparently because they
"got away with it last time." As Commissioner Feynman observed, the
decision making was:
"a kind of Russian roulette. ... (The Shuttle) flies (with O-ring
erosion) and nothing happens. Then it is suggested, therefore, that
the risk is no longer so high for the next flights. We can lower our
standards a little bit because we got away with it last time. ... You
got away with it, but it shouldn't be done over and over again like
that."