While it’s true that often military developments eventually make their way to civilian applications, imagine that money was spent directly on development of in this instance a new type of civilian aircraft.
The military could still adapt the frame to their needs, and it would most likely result in a cheaper and more useful vehicle outside of helping to kill people on another continent. This would also mean much earlier and more widespread adoption than yet another patented concept locked away because the military wants to keep it for themselves for a few decades (until it’s obsolete).
And even if that development somehow ended up being less optimized than one the military would make, it would most likely still be leaps and bounds better than the eventual commercial derivatives again sold by private entities, optimized for profit.