Communism is used in a variety of meanings. Technically it's the utopian idea of a free and equal society where the means of production are jointly owned by all members of society.
Practically Marx had developed an idea of a historic progression along the lines of classes, masters/slaves, feudal lords/servants, capitalist/workers which progresses via a struggle between these groups and which moves from the rule of the few to the rule of the many and ultimately to no rule of anybody over anybody else. The later stages being called socialism/communism.
Though most of what he wrote about did not concern how that would actually look like, but rather how the current system (emerging industrial capitalism) works and why it doesn't, as well as preparing the proletariat for a revolution to achieve the conditions for the next step in this progression which is something to be determined by those who face the problems of that society.
Yet things went different revolutions were put down, the problems persisted Marx died and industrial countries rather went for a salami tactic of giving out workers rights a slice at a time rather than suppressing them completely and risk a revolution.
Meanwhile in Russia (~1900), there was still a czarist government industrialization was just about to start and democracy was still out of reach. In that context Lenin got the ok of his party to build up a vanguard party of professional revolutionaries to kick start the revolution. He was apparently so thrilled of having gotten a majority once (didn't happen again after that), that he called his groups "bolsheviks" (majority). He wasn't particularly successful and got himself imprisoned and exiled quite some times so that he basically missed all the important revolutions in 1905 and 1917 and only after the last one was allowed to return.
Upon which he tried again to destabilize and use the existing destabilization of a losing WWI to seize power in a second revolution or coup d'etat in that year (1917). He held elections and came in 3rd, claimed power nonetheless and went straight into a several years lasting civil war. Where he not only fought counter revolutionaries but also those other leftist parties more popular than him. Then he died and Stalin took it from there, wrapping up Lenin's ad hoc political activism into a doctrine called Marxism-Leninism, which ended up being the blueprint of a "pre-capitalist socialist revolution" and the playbook of "communist parties" around the globe. It wasn't particularly great and even those who adopted it usually had to amend it to their actual situation. But after all Russia/USSR was the most powerful state level actor in support of communism and claimed the supreme role in that "international" idea. So did China after Stalin's death which led to them not getting along very well.
That their own systems were still far away from that utopian ideal didn't deter capitalist countries from calling it "communism", especially when it was authoritarian and failing.
So when talking about "communist parties" in the 1958 context you're talking specifically about Stalinist (Marxist-Leninist) inspired party systems. Rather than the general communist ideal.
Also after WWI the U.S. and the USSR engaged in a cold war, where Russia tried to erect a buffer zone of countries between them and the west and where the U.S. tried to push back or contain the "spread of communism". So you essentially had 3 blocks:
- 1st world (U.S. et al)
- 2nd world (USSR et al)
- 3rd world (neutral), 4th world (neutral and poor).
This includes borders between states, but also borders within states, like how the U.S. and USSR which had been allies in WWII had split Japanese occupied Korea or former Nazi Germany into 2 parts one controlled by the USSR and one by the U.S. or other Western countries.
And while these blocks avoided to engage each other directly they fought several proxy wars. Like when the North Korean dictator tried to invade the South Korean dictator and each side got support form the U.S. or the USSR.
Meanwhile WWII has left most former European colonial superpower pretty devastated so for example France wasn't able to keep it's rule over Indochina, not even with the aid of the U.S. which then gave rise to Laos, Cambodia and a temporarily split Vietnam which also resulted in the Vietnam proxy war.
So there were plenty of battlegrounds where the USSR offered a newly emerging state or potential candidate for a revolution their "successful" model of a pre-capitalist people's revolution, while the U.S. "bravely defended" the dictatorship of an autocrat as long as that meant that the country would not fall to "communism".
So with respect to Huxley, there was a pretty good chance that the combination of being overpopulated and underdeveloped would lead to internal problems, culminating in societal struggles and revolutions supported by the USSR and geared towards a Stalinistic system or that they would be controlled by a dictator who opens up his resources "to the free market" and erect some kind of banana republic.
Now with regard to totalitarianism. On the one hand it's a fighting term trying to denote the lack of "economic freedom" as the economy is state controlled and there's not much out of state activity. That on it's own however would just be a different system of governance and not even necessarily authoritarian if it were to be bottom up as intended (it more often than not wasn't).
On the other hand the concept of a vanguard revolution, in addition with the ideological commitment to "class struggle" the over interpretation of the "dictatorship of the proletariat" and the ideological focus on preparation to fight the counter revolution has contributed to a toxic paranoia giving rise to a terror and surveillance state that had many enemies and due to it's actions probably would have never seized to make new ones.
Also if one mobilizes the entire society towards one goal with no regard for the individual, then it's almost inevitable that some faction of the population will be in a position where this doesn't work for them and where they end up being an enemy not even necessarily by choice, but simply by circumstances. Though again the problem isn't necessarily large scale projects, but how you deal with these complications.
So with respect to overpopulated and underdeveloped countries that revolt because the situation is shit and thus cling to a minority party savior, likely with external support that is not necessarily interested in the well being of that country, is likely going to end bad, because even if they seize power they are likely not going to transform the country fast enough to solve the actual problems that lead to the revolution in the first place and if they can't do that they are almost bound to end up in a cycle of terror and propaganda to uphold their power and the more fragile the system the more it's likely going towards curbing resistance wherever it could start, even if their ability to do so is likely more felt than present.
Now it depends on how you define overpopulated and underdeveloped and luckily that cold war phase has ended or at least taken a pause. Some countries also managed to leverage their support into becoming self-sufficient. Not to mention that some lists even list the USSR as no longer totalitarian after Khrushchev:
So he might have lost that bet, but it probably wasn't too far fetched of an idea for the time.