The person you're replying to is insinuating that Facebook hires half-a-million dollar engineers based on diversity quotas instead of technical chops. No sense asking them to elaborate since they're obviously completely outside the company and have no worthwhile insight into their hiring practices.

The intern wasn't the single point of failure. They just triggered the failure. This should have been obvious at the design stage and pre-mitigated.

And if they don't mitigate it now, every hacker with access into their network now knows how to bring the whole show down in an instant.