I agree with
@vostok to some extent. The Soviet Union certainly collapsed of its own weight, but Ronald Reagan and other western powers(mainly France and U.K) helped speed up the process.
We should not forget that Because of the high oil prices of the 1970s the Soviet leadership avoided serious economic reforms, such as those that saved Deng Xiaoping’s China.
Instead, it relied on oil revenues as a means of keeping its decrepit economy going.
So by the early 1980s the Soviet Union was becoming a hollow shell, with an unreformed and increasingly backward industrial base producing outmoded pre-computer armaments.
This made the U.S.S.R vulnerable to what western powers and mostly Regan were planning against her.
In fact , a central instrument for putting pressure on the Soviet Union was Reagan’s massive defense build-up, which raised defense spending (for the so called 'star wars' fictional project and increase in nuclear warfare modernisation) from $134 billion in 1980 to $253 billion in 1989
. This raised American defense spending to 7 percent of GDP. Yet in its efforts to keep up with the American defense build-up, the stupid Soviet Union was compelled in the 1980s to raise the share of its defense spending from 22 percent to a whopping 27 percent of GDP, while it froze the production of civilian goods at 1970 levels.
. This coupled with Afghan war where western powers and the U.S spent almost a billion dollars a year providing the Mujahedin with portable surface-to-air Stinger missiles, which proved devastatingly effective in increasing Soviet air losses (particularly helicopters, and other fighter jets), while the Soviets according to one estimates spent almost 5-6 times more, helped bankrupt the Soviet union.
The final nail in the coffin for the Soviets was also Regan's role in using economic policies to weaken the Soviet Union by helping bring about a drastic fall in the price of oil in the 1980s, thereby denying the Soviet Union large inflows of hard currency it needed to sustain its econony and defence Spending.
Oops.....we should not also forget that role played by our former ally China.