The first two of the three O-ring seals were failing regularly.
...
No they weren’t, but the engineers knew they couldn’t take the cold.
NASA management also knew the Apollo 1 fire was likely. They also knew that a foam strike could be deadly and that Columbia was struck. They didn’t care. While Columbia was in orbit, another Shuttle was on the pad that could have been launched to rescue the Columbia crew.
My recollection is that it came out over the next few months that there had been incidents of burn through of one or more O-rings, but that it hadn’t made it through all three.
The eruption of exhaust gas through all three O-rings caused an immediate and measurable decrease in SRB internal pressure. This was seen in the Challenger telemetry data. It also caused a visible plume to be emitted from the SRB body; if that had happened before the Challenger explosion, I’m sure it would have been made public by now. Space shuttle launches were well covered by long range cameras all the way to the point of SRB separation.