Chernobyl contributed to the fall of the Soviet Union by damaging the economy and eroding trust in the Soviet system. Most certainly it was Gorbachev that led to the downfall and collapse of the Soviet Union he downgraded the military from super power status by reducing the USSR and dividing it up into the various states. He is hated even today by Russians and was refused a state funeral. Only the `west liked him. So he was not a symptom as. you suggest but he was the cause of the dissolution of the USSR.