The Soviets trying to take over Afghanistan gave us Al Qaeda.
The oddball part of this is, that while it's very important strategically for Ukraine to remain sovereign, who the fuck cares if the Soviets take Afghanistan? It would probably have been a huge drain on their resources to control Afghanistan, it's a backwater with no real natural wealth other than opium poppies. Then a few years later it would have become a sovereign nation again.
Putting any resources into stopping the Russians there was a net negative. Unless you're an arms dealer.