I think you need to educate yourself on what communism is and what democracy is. One is an economic system, the other is a political system. A country could have one, the other, or both. Certainly one cannot triumph over the other as they do not overlap even the slightest bit.
The conflict you are referring to is "Communism vs. Capitalism" and that is most certainly about money. Communism being introduced in a country where foreign corporations control 99% of the wealth and everyone else is poor, is most certainly a threat to the assets of those corporations. Whenever this situation has presented itself in the last 100 years, the foreign countries where the corporations come from have always stepped in militarily to preserve the status quo, i.e. keep the lower class in check.
In the case of Vietnam, they had both Communism AND Democracy. The reason we went to war against them was not because of the Democracy part, but because of the Communism part. If they had Capitalism and Democracy, then we wouldn't have cared. In fact, if they had been a brutal dictatorship, but still had Capitalism, we still would not have cared. A good example of that is our overthrowing of the democratically elected Allende government in Chile and the installation of the brutal Pinochet regime. The issue was Communism vs. Capitalism. Politics was not an important consideration in that decision, as they traded democracy for dictatorship in the process. Similar situations have also presented themselves in Brazil (1964), Iran (1953), and others. In each case, the US overthrew a democratic communist government, and replaced it with a capitalist dictatorship.
As for Vietnam, that war was 100% about economics, and 0% about politics or religion.
Just about all of the wars we have fought since WWII, and there have been dozens of them, have been of a similar mold. WWII itself was in fact of a similar mold, with the major conflict being Fascism vs. Communism -- again with Communism being a threat to the assets of the wealthy elite fascists.