Starfish Prime and Operation Fishbowl

It's still mind-boggling that the US detonated massive atomic bombs in the earth's atmosphere. Starfish Prime used a huge 1.4 megaton bomb.

Of course, these "tests" comprise the clearest evidence of the quarantine on the earth, and of the monsters here trying to break out.

Why else would humans contaminate the planet's atmosphere with radioactive fallout in such a risky way?