Two things can be true at once:
A) Diversity hiring is unrelated to the crash
B) There is a real scandal with hiring and the FAA
What I have read so far about this situation is outrageous. My understanding is that in 2014, Obama appointed a head of the FAA who wanted to diversify the workforce.
They introduced a biographical questionnaire which had rather arbitrary criteria for passing. It appears to have been explicitly designed to fail people that do not know the magical answers. The failure rate was 90%.
This is not the only example, but perhaps the most egregious questions: you are asked what your best subject was in highschool. If you answered science, you get 15 points (a substantial amount). No points for any other subject. Next, you're asked your best subject in college. If you answer history, you get 15 points. No points for any other subject.
Here is an alleged recreation of the test: https://kaisoapbox.com/projects/faa_biographical_assessment/
There are supposedly voicemails in which they helped select candidates pass this biographical questionnaire by providing their preferred race/gendered candidates with the answers. I haven't been able to find a voice mail online, but Fox Business reported that these voicemails exist.
Per a 2016 Yahoo Finance article, an internal FAA report falsely cleared the employee of wrongdoing.
It's my understanding that there is currently a lawsuit making its way through the courts regarding this. It's also my understanding that some allege that the problems are not all resolved yet with hiring, despite the questionnaire being withdrawn in 2018. I'm not sure of the specifics of how there may still be problems with hiring and the FAA.