The rubber o-rings weren't "poorly built", they were launching well outside the design parameters for temperature. Roger Boisjoly and other Thiokol engineers tried to warn them, but Thiokol management overruled them because they didn't want a huge publicity event to turn into yet another scrubbed launch.

The engineers knew in 1977 it wasn't safe to operate at those cold temperatures. Management of Thiokol and NASA didn't give a shit because they wanted their "Teacher in Space" moment. And they killed seven people.