Re: Always bad decision...
NASA was required to be adversarial towards suppliers, so if a supplier said a part was safe then they would have to prove it has a less than 1 in 271 chance of failure.
But the wording of the rules set by congress meant that if a supplier said a part was unsafe, then NASA would require them to prove the chance of success was less than 1 in 271.
NASA management were exploiting this obvious poor wording of the rules to regularly use components out of spec. NASA was (and still are) under pressure to launch missions on time, delays could mean missed launch windows or even project cancelation. So the wording of the rules was seen almost as permission to ignore technical specs and 'just get things done'. Challenger was the culmination of this cultural rot.
They launched even though conditions were outside the limits of 2 different parts of the technical spec, the minimum temperature, and the maximum wind sheer. The strong wind sheer during the launch bent the SRB further weakening the joint of the SRB sections. Later simulations showed that without the wind sheer it likely would have survived the o-ring failure.