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It's quite long, but I recommend this talk by Vijay Prashad where he talks about, among various topics, the effects of the fall of the Soviet Union on various communist parties around the world (the first five minutes or so are an introduction that you can skip).
In short, by the time of the fall of the USSR and other Eastern European communist nations, communist movements in the rest of the world had already diverged and begun forging their own paths. In India for instance, the communist party had already split over the notion the USSR was too 'paternalistic' and didactic - that while it had an incredibly valuable role both as the first socialist nation in existence and as a supporter of communist movements internationally, it shouldn't try to assert to communist movements in other parts of the world what their programmes should be. So by forging their own path based on their own conditions, other movements 'survived' the fall of the USSR by simply focusing on continuing to fight their local battles.
However, as Vijay Prashad also says, in the west the left collapsed totally. Every social-democratic party, such as the Labour party in the UK, totally surrendered to neoliberal capitalism and just positioned themselves as better at steering the boat than their further-right opponents. Mainstream western "leftists", even some so-called communist parties, are mired in condemnations of both historical socialist states and current anti-imperialist movements, as well as being infested with reactionary brainworms (transphobia, "anti-woke" etc.) So in that regard, in the west they didn't keep optimistic.