Although your general point about the import of religious ferver is well taken, I cannot agree with this attribution. The Soviet Union fell because its economy collapsed, and after a while it bacame clear even to the ruling party and the KGB that repressions and slogans would not revive it. In particular, this is what has become clear to Gorbachev (the ruling party member) and Chernenko (KGB, Gorbachev' mentor and backer). Due to these two factors, repressions were called off. Then MULTIPLE liberating sources, including the Church, came into play.
Your remark made the church look like the reason for the collaps. This is very far from the truth, with all due respect.