The Challenger accident was caused by some extremely poor decision making by NASA poobahs, who were under the gun to get a Shuttle into the air.
NASA's own procurement specifications for the solid rocket boosters called for an ambient air temperature of 59 degrees F or higher at launch time!
Morton Thiokol engineers pleaded with NASA not to launch because they knew the rubber gaskets would burn through (in fact there had been some small burn-throughs in the gaskets previous to the Challenger disaster). All occurred on cold weather launches, but no Shuttle had ever been launched in thirty degree temperatures.
Cold weather shrinks things, and no amount of PR bullshit will change that inconvenient law of nature.
At the time the Challenger was launched, the ambient air temperature was in the thirties; the temperature at Cape Canaveral had been below FReezing for several hours prior to launch; and there was excess ice all over the solid rocket boosters, the main tank and Challenger (it had also rained).
Bottom line, a very poor (criminal IMHO) NASA Marketing decision was the direct cause of the accident!