This was a deliberate decision back in the 1980s and 1990s related to how to structure personnel. You'll likely recognize it as how software teams are siloed and the concept of "full stack" is kind of a misnomer.

The theory was basically that complex systems needed specialization for building and maintenance and that the US military could not afford or recruit the kind of people that could simultaneously run operations, do management AND troubleshoot.

In other words, military personnel are not seen as technical experts that focus on one thing for a decade, moreso that they are like project managers who have depth in one area from their first 5-6 years and then "broaden" out to fill in the management layer of the force beyond that.

There are exceptions to this of course, warrant officers and the like. However it's a tiny slice and given how massive the system is and how many sub-systems are involved - the management layer grows in the form of uniformed ranks while the technician layer grows in the contractor ranks because of how the force is structured.

The incentive for that contract force however is to keep the contract (and follow on) and the knowledge related to it, so they end up building in these kind of "nobody can touch this but us" requirements. Functionally you can see how this is a self fulfilling prophecy - we aren't recruting or structuting our force to have the capability to maintain systems because we have a contract force that does it.

To fix this a deliberate decision has to be made to change the force structure to build more technicians and unfortunately people like that don't want to take the pay and lifestyle cut so we just can't fill out the ranks.

I could go on all day, including how the defense industrial base as well as citizens balking at growing the size of the uniformed forces reinforce this system, but it's a pervasive problem across multiple vectors.