Two big props to the Soviet economy were oil and gold. Much of their foreign exchange came from these two sources. Under Reagan, private gold ownership was restored which brought a flood of gold purchases, especially South African Krugerrands. Then, the Saudis agreed to increase oil production. The result-both commodities tanked in price, undercutting the Soviet economy and stimulating ours.
It didn’t help either that we effectively made China an ally at the same time. The American connection enabled the Chicoms to build up both their military and their economy, both of which at the time were in a rudimentary state. All the while, taxing the capabilities of their neighbor.