You should have stopped to think about why such a person was hired in the first place, while there are an endless supply of very talented, hard working, and honest young people who would never be given a chance at all.
But if I guess right, hiring is not seen as the responsibility of your company. And that's the core of the problem.
The hiring process is probably barely better than random, and, probably even closer to random for a junior hire.
Junior hires mostly don't know anything. So, you're pretty much hiring on "seems smart, curious, and enthusiastic" and praying a lot that you can train them. You're simply going to get misses.
This is one of the advantages that you get running "cooperative engineering" programs. You get to vet juniors before they get welded into your pipelines.