There are so many companies building airship prototypes of similar scale, Occam's Razor suggests its benign. It's like seeing your first satellite and being convinced it must be military.. This isn't the Sputnik era of ballooning by any stretch.
So you think that a private company produced a high altitude airship prototype that just happened to go on a journey thousands of miles across the world and over a number of us military installations?
I genuinely cannot understand how you think that's a simpler explanation than it being a surveillance platform.
(btw the chinese press tried to claim that it's a weather balloon, an obvious lie)
It didn't go "hover over" military installations. It went over the Rocky Mountains. Pretty much any balloon that crosses the US would go over "military installations" especially when USG can't confirm where these installations are even located (they therefore must suggested that it did, game theoretically).
Wouldn't any legitimate airship have some sort of required transponder or tracking beacon? If that had failed, wouldn't a responsible company step forward and identify themselves once it became an national security incident?
https://aviationoutlook.com/airship-manufacturers/