I agree. The Challenger Disaster was bad, but the Columbia Disaster was worse. They already know before flying that the designs has many problems, they know before reentry that the thermal protection was potentially broken.
> NASA management referred to this phenomenon as "foam shedding". As with the O-ring erosion problems that ultimately doomed the Space Shuttle Challenger, NASA management became accustomed to these phenomena when no serious consequences resulted from these earlier episodes.
This is most relevant sentence of https://en.wikipedia.org/wiki/Space_Shuttle_Columbia_disaste...
> NASA management referred to this phenomenon as "foam shedding". As with the O-ring erosion problems that ultimately doomed the Space Shuttle Challenger, NASA management became accustomed to these phenomena when no serious consequences resulted from these earlier episodes.