e.g. No intern that needs permission to get a box of pencils from the supply closet should ever be fired for putting a mistake into production that costs a company $100,000. If a company loses $100,000 on a mistake, you look to the person in the hierarchy who manages budgets of that size. It's their job to make sure the safeguards are in place to prevent losses like that.

In government it's difficult but not impossible to put a dollar value on losses like this. In this case, whoever was in charge of that network, and could request budget to build safeguards (whether software or training) against such mishaps, was ultimately responsible. Firing the intern is just shit rolling downhill.