Communism's fall was set into motion by Russian paranoia of foreign invaders. The Russians had been invaded by Bonaparte, the Kaiser, and Hitler. Not to mention some battles in the USSR's infancy when Western nations tried to overthrow those Soviet bastards who stole power. As WW2 was raging, the allies had loose talks of how Europe would be handled after the war. Stalin was extremely eager to restore the territory of the old Russian Empire as well as create buffer Slav states. There is that connection of ethnicity and Cyrillic based language. Stalin was paranoid of another invasion, and not as much of the ideologue looking to spread Communism like others in the party. With client states to the west, the Russkis could have a 100-250 mile warning before an invader entered the Motherland. The problem was that in the devastation created by WW2, these countries would need to be supported by the country with which they were aligned.
After WW2, the US used the Marshall Plan to help rebuild Europe and help create friendly democracies. The Soviets didn't have a plan. If you read books of post-WW2 Russian life, it's horrible the recovery of the common folks as Stalin & his cronies stayed up all night eating, drinking and watching movies. Like so many other events in history, the dissolution of the Soviet Bloc also has its roots in economics. With a state controlled economy, they did not have the free enterprise or innovative spirit to both serve military and consumer desires. Waiting lists for cars and washing machines were years long yet new tanks & planes were quickly built for an invasion that would never come. As I typed in a previous entry, the Soviet's oil wealth fluctuated and created a roving bear or a hermit bear. Oil was how they earned hard Western currency. That was how they funded the spread of Communism elsewhere. That was how they kept Eastern Europe in line. It should not come as a surprise that as oil prices collapsed in the 80s, Russia ran into problems. There was a connundrum that even Reagan wrote of in his diary while in office: why give loans and aid to the Soviets to prolong a system that oppresses people? The West Germans did this with East Germany in 1983 with a multibillion mark loan. Some argue that this delayed the fall of East Germany and reunification. Even in a Commie nation, if you can't pay people or keep the lights on, you're going to have civil unrest.
It would be foolish to overlook the efforts of individuals in the struggle. Lech Walesa was a figure of renown who started strikes in Poland in the early '80s, which eventually lead to Communism's downfall in 1989. The underground work of the Solidarity movement also allowed for a force to be present as the Commies dissolved preventing a power vacuum, which can sometimes be worse than oppressive Commie thugs at the helm. Organized Christianity is often criticized by people for the horrible acts committed in its name (stuff hundreds of years ago, and God forbid any celeb cry out about modern terror in Islam's name). In Poland, tremendous support was given to the Solidarity movement by Pope JP2, himself a Polish citizen, which acted as a benign foreign power where the US could not directly interfere. Vaclav Havel is another name, in the Czech Republic, who spoke out on the international stage as well as his home country against the Commies. Each opposition party and overthrow starts with one voice, and he was an early and loud voice. He continues the struggle for basic human rights for all. Havel is the type of person the world could use as Secretary-General of the UN, but he is too pro-Western Democracy to be elected. These were front line soldiers in the fight for human rights, and they deserve worldwide respect.
Lastly in the ideology battle, Thatcher and Reagan took a hard stance confronting the Soviets. Part of this approach was appealing to the Russian respect for force & strength. Project an image of power to get them to respect our stance of standing on the side of freedom, human rights and individual choice. Reagan fought Communist ambitions in South America & Africa (sometimes in a dirty fashion). No more detente with the Soviets (I will give Nixon credit for detente & the manipulation of the schism between the USSR and China). Confront them, harass them, and expose their policies for the oppression & terror that they were. Reagan's "tear down this wall" speech was a challenge that if their system truly was better, the Commies did not need a wall to keep their citizens in. Reagan pushed Gorbachev in all of their discussions to allow greater freedoms for the Russian people as simple as freedom of religion or an independent press. It should not surprise anyone that the Nobel committe gave Gorbachev a Peace Prize in 1990 for his efforts between 1985-90 and jack squat to Reagan, as if there was not another side to every nuclear arms treaty Gorbachev signed or the ideological battle he waged in the Communist Bloc nations. Nope, Gorbachev did it all by himself without any prodding.
Twenty years later, the world can look at the Soviet system of Communism as an aberration in human history as an economic system. Truly evaluating it for what it was, we can see it as totalitarianism masking as the collective will of the people. Communism was an excuse for Stalin to run the country as the Tsars had done so before him. After his death, the power was a bit more like an oligopoly. Still horrendously oppressive, but not tied to one man's whims as much as under Stalin. It was more about maintaining the elite in power at the expense of individual achievement and freedom. It is unfortunate that Stalin's paranoia, as well as Kruschev and Brezhnev continuing his terrible policies**, kept Eastern Europe and to an extent the World hostage to such a horrible system. Now we can look back and be thankful for an end to such a horrible system.
** Kruschev's rival for power after Stalin's death was Beria. Beria was a torturing, sadistic animal. The worst story I recall reading about him was telling a beautiful young woman he'd free her family members in the Gulag if she had sex with him. She meets him, he rapes her and then afterwards says (paraphrased) "i forgot, they died about a year ago in the camps". Despite being a horrible human being, he had ideas of individual property rights, openness, reunification of Germany and other moves which would have to wait for 30+ years. Beria saw those moves as the only way the Russkis could compete. He was an outlier. He ended up dead.