but it's a logical conclusion that the best location for telescopes (of any kind) are low humidity desert locations
I would replace your parenthetical part with (optical and infrared). Optical telescopes favor dark skies far from urban light pollution, as well as stable and transparent air which is usually found at high altitude. Hence they tend to be located on remote and arid mountain summits. Infrared observations are hindered by the absorption of IR by water vapor in the atmosphere, so they favor high altitude as well. Put the two together, this is why most observatories are located where they are. But the radar functions of Arecibo's large dish aren't affected by light pollution, humidity, or even clouds. They go right through them.
Consider the Greenbank radio telescope in West Virginia. It would not be a particularly great location for an optical observatory, because it's often cloudy. But it doesn't care about clouds, and it does care about radio interference, which is why the area is a radio quiet zone.
Ah, geopolitical....so now we see what's going on here. That location had very little to do with science. I intensely dislike it when any kind of politics or military BS taints and corrupts science, same as with corporate influences.
It had a lot to do with both, and the choice in location ended up producing nearly 60 years of excellent science -- both for missile defense and for astronomy. I think it's rather fortuitous that a project that had military applications also had such significant and broad astronomical applications, and captured the public's interest as much as it did.