It's worth remembering that Chernobyl wasn't the only disaster driving public distrust. Chernobyl is just the most known and mythologized one in the West, but there were three in relatively quick succession during that period: Chernobyl (1986), Spitak earthquake (1988), and Ufa train disaster (1989). All three (and the government response to them) had huge resonance among Soviet population, with Spitak surpassing Chernobyl.