I don't think you can solely blame DEI, nor can you put all the blame on the appointed head of the National Space Council that everybody seems to have forgot:
https://www.space.com/national-space-council-vp-kamala-harris
But I'm sure they have had an impact. You combine a bean counter leader of Boeing, fixed price contracts where non contributing deadweight is hired to meet quotas, and lack of competent government oversight at the top and you set up a situation ripe for failure.
I'd blame this one 90% on Boeing leadership, 5% on DEI and 5% government leadership. My percentages are admittedly completely made up numbers.