The Domino theory was complete bullshit. The problem was that western thinkers completely ignored how extremely exploitative colonialism had been. These thinkers saw USSR corrupting the world with communist propaganda, like a pedophile with a van full of free candy. But the west was doing it to themselves. All USSR did was to present
any other alternative story than European and American benevolence.
It can't be emphasized enough how delusional the European and American public was on the impact of colonialism was around the globe. In the 1950'ies they all bought into the White Man's Burden story of how white people brought brown savages civilization, and how the "natives" should be grateful. This narrative was actively pushing ex-colonials straight into the arms of USSR.
This only stopped in the 1980'ies when the Western mainstream narrative on their colonial past switched, to us partly taking responsibility for our actions. Very few people in the west today think that colonialism was great for their colonial subjects. But even in the 1980'ies the idiotic public of Europe and USA having a common narrative of that free market capitalism works just as well in a modern democracy with a non-corrupt judiciary, as it would in a kleptocracy propped up by CIA. Further pushing the ex colonials into the arms of USSR.
The spread of communism after WW2 is directly linked to the colonials trying to break free from western dominance and turning to the
only source of weapons, with which to fight their colonial overlords. The west did Russia's work for them. All the western powers needed to do to stop the spread of communism was to stop throwing gasoline on the fire. Which is what we stopped doing in the 1990'ies, when USSR fell.
The wests fear of USSR created such a bogey man that we scored in our own goal.
en.wikipedia.org
But as industrialism and information age technology spreads across the world, dampening Europe's head start, we will get a world with wealth and resources more spread out over the globe, this will just sort itself out. Colonialism, and the cold war could only have happened because the wealth gap between the poorest and richest parts of the world was so extreme. Creating all kinds of knock-on effects. Those effects are disappearing now