While I probably agree, why can't the Major just be the project manager and he or she consults daily with their trusted, deeply responsible technical advisor who is actually from the industry?
Former USAF officer here. Part of the problem is that a Major or Lt Col does not have the rank or budget necessary to pull off a project of that scale. They are still too low on the chain, and too easy to override and then scapegoat when the project fails. Moreover, the officer system is "up or out" meaning that a field grade officer will always be incentivized to prioritize short-term paper gains over long-term strategic gains. This is a bad thing when designing critical infrastructure. A more senior officer with longer tenure and a bigger budget (i.e., a General or SES) needs to run a project intended for millions of users in a defense context.
What's stopping the PM-but-really-Major from invoking chain of command and making overriding decisions? In an org like the military I'm not sure you could just say "please act like a PM and don't make broader decisions" to someone with seniority and expect them to not exercise their authority, unless you actually revoke their authority.
Or, what's stopping the Major from installing a friendly and symbolic tech advisor? Stranger things have happened than bureaucrats hiring and building departments designed to do nothing but legitimize and push forward their own agenda.
Because the major is unqualified to evaluate the guidance they receive. Same reason we don't randomly pick our battlefield generals from a pool of chimney sweeps.