Framed this way, I'm not surprised younger Elon's company missed it.

It would have been much more economical to test a coupon of the material upon receipt, like what is considered standard practice throughout aerospace companies. Or, like you said, you can blow up a rocket and launch pad instead. Same result, different risk profiles.

The question is how you transition from the state of not knowing to knowing.

If you have poor processes and a lack of knoledge, how do you get better?

In this specific instance, the root cause analysis and remediation are vastly more complicated that presented in this thread. It is not like SpaceX wasnt doing testing on incoming materials at all or ignorant of the concept.

Regarding knowing if you have a poor process or not, it depends on the uniqueness of your problem. For proteins that are relatively common, like material checks, you can shorten your learning process by looking at other organizations that have been through it for decades. For more exotic non-standard problems, you might have to learn the hard way.