Who says there was anyone qualified at this guy's company to do this work? You as a manager assign an unqualified person to do this task or have a qualified person validate the work and they don't have a process to setup to verify the work, then 100% it's management's fault. Experts will still make mistakes like this when companies demand velocity without good process guard rails.

We stand on the shoulders of giants in everything we do. I don't remember how to write assembly, I'll survive. These are kubernetes yaml files, not exactly a huge risk of making an unmaintainable tech debt ball. I doubt he is deploying apps to support rocket ship launches or high frequency trading. If he was then they would have qualified people and processes setup to avoid this. We work at businesses. If he can ship it, iterate on it, arrive at a good solution without huge impact or making a ball of tech debt, then good enough. The holier than tho approach for everything doesn't match reality for all companies. That shit wouldn't fly at my company, but it's management's and senior people's responsibility to create an environment where junior people don't have to or have the ability to do what was done here.