Were people aware of the tests the government was conducting on its population? Was there some giant exposé I'm not privvy to? Or did everyone's dad who lived within a thirty-mile radius of Los Alamos start getting cancer at the same time, and they subconsciously connected the red string on the corkboard?

Really, why did the paranoia turn inward? Did the Cold War just go on too long? Everyone was sick of their taxes going towards the stockpile while the first question at the hospital was whether your insurance premium payments were up to date? Consider the blob as the physical manifestation of how the powerful consume everything and everyone for reasons too insane to parse anymore. 

Who better to fight it than young greaser Johnny Drama with a mullet looking like proto-James Hurley?