Ok, so let's take the grain of truth and actually examine it and see how many lies of obfuscation fall out when we do...

It's true that many developing countries experienced significant increases in life expectancy during the 20th century. Some of the main reasons this happened was due to global advancements in medicine, public health measures, and improved living standards. It should be noted that the USSR led the way in these, being as focused as it was on such things as using state capacity to improve public health (and this despite the massive losses it incurred while defeating the Nazis and liberating western Europe from them, resulting in the decimation of an entire Soviet generation. But this is another remarkable communist achievement for a different post). Most of what we're talking about here was before the era of neoliberalism in the west, so capitalist countries weren't as outright opposed to things like public health at the time, but it was still a distant priority behind profits and domination. Public health tended then, as now, seen as merely a means to the end of capitalist accumulation rather than valued as an end in and of itself. One should look into the USSR's drive to cure smallpox, and how its eradication would not have been possible had it been left up entirely to the US, but that's another digression.

The statement from the comment above about how 'this improvement in Chinese life quality was actually a phenomenon happening all over' paints with too broad a brush, so ridiculously broad as to cover up all the relevant details and thus reality of the matter which is that there was tremendous variation in progress across the world. While the overall trend of increasing life expectancy is common, the rate and timing of improvement varied significantly between countries. China's progress was astounding in how rapid and substantial its progress was when compared to other developing nations. And the fact that it happened coinciding with the victory of the PLA, the leadership of the CPC, and their founding of the PRC, should make it obvious why this improvement was suddenly able to happen, and not some fluke coincidence as was laid out by u/isa41. Since it was the country Nigera that was brought up by the know-nothing let's go ahead and use Nigeria as the example to consider this variation.

Nigeria did indeed see improvements in life expectancy, but its trajectory differs drastically from China's. Nigeria's progress was and has been slower and less dramatic, full of "fits and starts." In the 1960s, for example, Nigeria's life expectancy was below 50 years. It has improved since then, but as a slow incline and nowhere near as rapidly as China's, which the graph that @BeamBrain@hexbear.net posted shows. I haven't gone around to find all other countries life expectancy graphs just to write up this reply, but I would bet that if I challenged someone to find a graph (that isn't fudged or manipulated obviously) that shows the kind of rapid progress and on such a grand of a scale as China, they would not be able to find one. Well, someone might... if they found one for the USSR, just set back a few decades. Because the only other place where you can find that kind of rapid improvement sustained over that length of time for that many people would be the Soviet Union.

What this liberal ideologue is trying to cover up here is that what is so astounding about this graph is not simply that improvement happened, but the degree of it. The sheer number of people involved and importantly the rate of change (first derivative). The agenda to discredit the jaw-dropping achievement of the CPC in improving the lives of the Chinese people becomes as obvious as it is odious.

The fact of the matter is, the steep incline in China's life expectancy in the late 1940s and early 1950s was more pronounced than in any other developing countries. This rapid improvement was influenced by specific policies and initiatives implemented by the new government, including widespread public health campaigns and improvements in basic healthcare access, as well as education that included teaching about healthcare.

Also, the statement about Nigeria being "plagued by famines" and following the same trend is completely inaccurate. While Nigeria has faced food security challenges, it hasn't experienced famines on the scale that China did in its history. To say otherwise is just lying. China's life expectancy trend did include setbacks, most notably during the Great Famine of 1959-1961, which is not typical of all developing countries, but they were always learned from and corrected for, something you won't see in countries plagued by capitalist exploitation which tends also to bring things like war and instability.

In short, don't be fooled by these losers with an agenda who are either sinophobes, anticommunists (which itself can't be separated from fascism it turns out), or just deeply misled people who simply can't accept that reality doesn't conform to their worldview and seek to distort the truth so that it better appears to. Seek to see reality for what it really is. Don't be a lib trying to wrap the world around your flawed idealist notions. Understand and apply material analysis.

The industrial revolution had already long since happened, dipshit. I wonder why at that very specific fucking time, China was finally able to industrialize the way that countries exploiting it already had. HMMM. Why might that come about then? Better put on my big thinking cap about that one.

"and modern medicine made its way into China."

HUH? Wow, I wonder why it made it's way into China right then? What a WACKY coincidence!

This trend could be in spite of Mao and not because of him.

Mao was following (and building upon) Marxism-Leninism which among other things is a science that predicts how industrialization occurs and can be used as a roadmap for how to achieve it. The fact that Mao followed and forged this roadmap with the stated intent to do so and that expected result happened is not a "trend in spite of" literally the policies you can look up that he (and the CPC) implemented with the purpose of achieving that very thing. (I'm facepalming so hard rn).

Correlation does not equal causation.

No, but you know what? Causation does equal causation, like when someone says "I'm going to throw this ball" and you watch them throw a ball, you can be pretty confident that the ball is moving through the air because their throwing it, which they said they were going to do and you saw them do, caused that to happen. Nah, it must be some other hidden corollary that is the reason the ball suddenly left their hand and moved through the air. Frankly it's embarrassing to see someone trying to come up with excuses to hand wave away the obvious fucking truth that is right there and plain for anyone and everyone to see, at least anyone who isn't frantically putting up blinders to try to protect their bullshit worldview.