Although NASA had flown twenty-four successful shuttle missions before STS 51-L (the official name for the January 1986 Challenger mission), other flights had experienced lesser versions of the same problem which caused the Challenger explosion.
Neither the astronauts, nor their families, knew about it.
But the manufacturer of the shuttle's solid rocket booster (SRB) and solid rocket motor (SRM) knew. So did some of the management officials at NASA.
But the people Boisjoly reported to wouldn't listen.
And the people who made the ultimate decisions at NASA weren't told.