Two things helped to destroy the empire. First, it was the attempt of the Soviets to keep up with Reagan's Star Wars. They lacked the resources.

But also, Congressional Representative Charlie Wilson, single-handedly helped to get appropriations (matched by Saudi Arabia) to defeat the Soviets in Afghanistan with CIA funding of the Mujahideen in the Soviet–Afghan War [1]. This was the Soviet Vietnam.

Tom Hanks starred as Charlie Wilson in the 2007 movie, Charlie Wilson's War[2].

The movie was based on the 2003 book, "Charlie Wilson's War: The Extraordinary Story of the Largest Covert Operation in History"[3]

Both the film and the book are worth watching/reading. Truly an incredible story.

Public facing Charlie Wilson was a playboy. Privately behind he scenes he was on two Congressional subcommittees that doled out black-ops funding to the CIA.

[1] https://en.wikipedia.org/wiki/Soviet–Afghan_War

[2] https://en.wikipedia.org/wiki/Charlie_Wilson%27s_War_(film)

[3] https://www.amazon.com/Charlie-Wilsons-War-Extraordinary-Ope...