"Causing" is a complicated verb to use for something as complex as the Chernobyl accident, and there were many "causes" of it. There are also many political stakes attached to assigning a "cause," so it has been hotly debated over the years, and indeed the last show-trial of the Soviet Union was in part devoted to trying to pin down one "cause" and excluding some others.

The most basic account of the Chernobyl disaster is as follows. There was a very large nuclear power station in the Ukrainian SSR that was commonly known as Chernobyl. It used a type of Soviet reactor known as the RBMK, which was designed to meet the needs of the Soviet state: it was a relatively cheaper reactor to build, was designed so that (if desired) it could be used for both military and civilian purposes (e.g., it could generate plutonium if desired), and it had far fewer safety precautions than other reactor types, because there was a sort of arrogance about the safety of nuclear power and Soviet nuclear engineers. It also had some very dangerous design flaws that were known about, but kept secret even from the plant operators, because the expertise to design and evaluate reactors was done by the part of the Soviet bureaucracy responsible for making nuclear weapons (where secrecy was habitual for design information) but the operation was done by the part of the Soviet bureaucracy responsible for generating electricity in all forms. So already you are getting a sense of how the Soviet context shaped the situation down to the very core technical context.

One of the safety features of the RBMK is that, in the event of a total power loss, there should be enough energy in the system to keep the cooling water flowing until the emergency backup pumps have time to turn on. The details of this are not particularly important, except that testing this feature was part of the Chernobyl plant's operating certification, and they had not gotten around to doing it for over a year, and so it was something they really wanted to get done. The way this test works is that the control rods are pulled out of the reactor and then the power is shut off, and in principle this should be fine. But they hadn't done it, and it was very delayed, and delaying was a bad thing because it meant that the reactor fuel load was near the end of its cycle, which in turn meant it was full of a lot of fission products, which meant it was hard to control and predict. Again, there are technical things here that are pretty complex, but the basic take-away is that they needed to do this experiment but didn't do it on time and as a result they were doing it under conditions that were very problematic for the reactor.

On the day of the experiment, the local Soviet government denied their request to take the reactor offline for the experiment during the day, because they needed the power. As a result, the test was pushed back to the night shift, which was a totally different group of engineers, ones who had not prepared or studied to do this particular experiment. But the bureaucracy dictated they needed to do it anyway.

The engineers did the experiment, and the power in the reactor got dangerously low, which would make it very hard to restart and control. Then it got dangerously hot because of other bad design elements and the fact that it was so late in the fuel cycle. They thrust the control rods back into the reactor, but didn't realize that one key feature of the RBMK (carbon moderators on the end of the control rods) would under those circumstances cause a massive spike in reactivity, which caused the reactor to explode, blowing its top off and spewing radioactive materials. I am abbreviating the technical aspects just so you can get a picture of it: these engineers who did not totally know what they were doing anyway took a reactor that surely should not have had this experiment done on it under any circumstances at this moment and made a fatal calculation that was related to a known design flaw that they knew nothing about because it was classified and because they had unwarranted faith in the reactor due to a Soviet culture of nuclear and engineer veneration. They made a bad call and it caused a massive disaster.

Even then, the engineers at the plant, and the plant managers, and their Soviet bosses, all were essentially in denial about what had happened for about a day, even as fire-fighters were rounded up to try and control the burning reactor core, which was venting radioactive materials skyward. There is a famous anecdote of one of the chiefs of the plant arriving to it and kicking a piece of graphite he found on the ground, cursing the employees for their leaving such a mess, not realizing that the graphite had been literally thrown out of the reactor and was highly, highly radioactive. It was an extremely deep level of denial.

All up the command chain this denial persisted for days, and even when acknowledged it still resulted in secrecy and a refusal to admit the disaster had occurred. A massive parade in Kiev was still held despite an awareness that the city was being exposed to large levels of radioactivity. The story was only acknowledged even a little bit after the radiation drifted far enough outside of their borders that non-Soviet states began to detect it, and even then, things like evacuation and cleanup were only slowly and fitfully pursued. The result is that many more people were exposed to radioactivity than should have been.

OK, so you look at a narrative like that above, and you can ask: whose fault was this? Was it the engineers who made the fatal mistake? Was it the local Soviet government that forced them to do the ill-advised experiment at an ill-advised time? Was it the designers of the reactor who put so many flaws in it? Was it the culture that made the engineers and designers believe they could not make such mistakes? Was it the government who created an institutional environment where mistakes could not be acknowledged even as they literally irradiated the people who were denying them? Was it the Soviet central government who refused to acknowledge errors and doomed many tens of thousands of its citizens to injury and even later death by exposure?

You can see that you could, to some degree, say "yes" to almost all of those possible candidates without too much hesitation, if you are looking at it as an outsider. There are other candidates for blame as well that have been offered up — e.g., there are many who say that Chernobyl is an inevitable outcome of nuclear power in general. You can see that there would be vastly different political implications in concluding that the fault of the accident was just the engineers working on it that day, versus concluding it was a product of the Soviet system in general, versus concluding it was a product of nuclear power in general. By "political implications" or "states" I mean, "consequences for belief or future action based on this conclusion." If you think Chernobyl is a result of nuclear power in general, the future implication then becomes, "don't use nuclear power." If you think it is the Soviet state, then it's "the Soviet state was a bad/incompetent organization." If it was just the engineers, then it's "these people were bad/incompetent," and the line of implication stops there. That, by the way, is what the last show-trial of the Soviet Union concluded: the problem really was just those few engineers, and there were no implications that might affect one's judgment about the USSR or nuclear power to be taken from Chernobyl.

So, anyway, you can see that there is a pretty good case to be made that the Chernobyl disaster was, to some degree, the fault of the Soviet government. That does not mean that they caused it directly, or deliberately, but rather that they created the technical and bureaucratic context in which the accident took place.

It is also of interest that a liquidator would have most likely been a Ukrainian, and in the development of an independent Ukrainians identity in the post-USSR, Chernobyl became a potent symbol for Ukrainians about the dangers of Soviet/Russian rule, as they perceived of the event as being caused on their soil by decisions made in Moscow.

On Chernobyl, much has been written, but I particularly found Serhii Plokhy's Chernobyl: The History of a Nuclear Catastrophe a very useful and gripping read. On the Soviet bureaucracy of nuclear power and the development of the RBMK design, as well as the details of the Chernobyl engineer's trial, see Sonja Schmid's Producing Power: The Pre-Chernobyl History of the Soviet Nuclear Industry. On the role of Chernobyl in Ukrainian independence, see Adriana Petryna, Life Exposed: Biological Citizens after Chernobyl.

Aviation accident investigations have a similar philosophy. Instead of finding THE ONE PERSON AT FAULT, they concentrate on the chain of failures.

The chain in an air crash is usually 7-8 links long. That many things went wrong in a specific order for there to be a crash. There are generally specific people responsible for each link in the chain.

But it's hard to assign overall responsibility because, without all the other links being in place, the accident would not have happened.

Concentrating on process, training, and responsibility is the best way to make people less likely to make their own mistakes.

It also means you have to have good employees, honest employees, and well-trained employees. It also means that you have to give them autonomy and authority to stop what they see as a bad practice. And you have to punish people who are not doing the right thing. If they fail multiple times, they have to be fired.

Because an airplane mechanic (for example) who doesn't follow process can go to jail for killing hundreds of people.