I read this article, and many years ago the full report, and one of the omissions on the list of causes that stood out to me was overcomplexity --- if you read about the possible functions of the machine, they really don't require multiple threads much less a full multitasking OS. None of these race conditions would've occurred if it was a simple single-threaded embedded controller.

To paraphrase an old Hoare quote, software can either be so simple it obviously contains no bugs, or so complex that it contains no obvious bugs.