What I realized later was that none of the civilian markets could possibly justify the cost of the project.
The particular type of signal fitting I was doing was only achievable by a few thousand expensive domain experts in the world, so, I think that addresses your other point.
A journalist not involved at all figured it out just fine, but at the very least it's not like it wasn't going to be a weapon.
Frankly though I wonder what the various judgemental people in these comments think about say, the tens of thousands of people who at the time were just straight up making artillery ammo.
Not to mention it itself requires a conspiracy theory: "no one would do this work voluntarily" (or "all the smart people have to be tricked because they're so smart they obviously agree with me").
As though people don't just go and work at Boeing or Lockheed Martin.
The much more common reason is compartmentalisation. Employees are told as much as they need to know, no more.
If someone can design a glide bomb without knowing that it has an explosive payload, then they're not told.
The fear is not so much the employees themselves (they might be quite patriotic!) but that the information will leak out to the enemy, giving them a chance to counter the weapon or copy it.