Challenger wasn't really about cutting safety margins, but about kicking the can on a known problem: blowby in the motor joints. It was a gut feeling by the engineers that the problem was related to temperature, but there was enough of a random element to it that there was nothing specific to point to.

That should have been enough to scrub anyway, but there was clearly political pressure to launch.

I do agree that they need to specifically design anti-fragile.