There are a multitude of reasons for why the holocaust is particularly noted as a genocide compared to others:
First, the colonial era perception of 'civilized' vs 'uncivilized' people factored. The holocaust was perpetrated by 'civilized' western folk against other 'civilized' western folk. The perception was that vulgar murder was something which was done in other places by 'lesser' folk. The holocaust forced society to reinterpret its understanding of human nature and civilization. The questioning of how western ideas could lead to the holocaust persists in the west, due to the self-centric nature of historical studies (this isn't a bad thing, per se).
Mass media. The Nazi movement and WW2 generally was a mass media movement. There is a massive amount of recordings of Nazi rallies, Nazi films and propaganda (not that there's much to separate between the two). There are photographs of Wehrmacht and SS war crimes. There are newspaper articles. They would broadcast Hitler's radio speeches worldwide. At the time, there was hardly a westerner who wasn't aware of the Nazi movement. By contrast, the Congo or Turkey didn't have the same level of media awareness, either of the perpetrator's existence and ideology or of the crimes they committed. The reproducability of such images contributes to people's fascination today: we can still go witness original footage of the Nazi movement in action. It feels more 'real' as a result and the crimes more visceral.
The context of WW2. Nazi Germany brought nearly the entire world into a massive war. As such, its an event most students will learn about in school, and therefore will learn about the holocaust and why it was perpetrated.
Lastly, Germany today doesn't resist knowledge of the Holocaust. In some cases, groups have cause to deny or resist proliferation of the knowledge of a genocide. This makes it harder to access information, and creates counternarratives which push back against understanding what happened.
Hi there! You’ve asked a question along the lines of ‘why didn’t I learn about X’. We’re happy to let this question stand, but there are a variety of reasons why you may find it hard to get a good answer to this question on /r/AskHistorians.
Firstly, school curricula and how they are taught vary strongly between different countries and even even different states. Additionally, how they are taught is often influenced by teachers having to compromise on how much time they can spend on any given topic. More information on your location and level of education might be helpful to answer this question.
Secondly, we have noticed that these questions are often phrased to be about people's individual experience but what they are really about is why a certain event is more prominent in popular narratives of history than others.
Instead of asking "Why haven't I learned about event ...", considering asking "What importance do scholars assign to event ... in the context of such and such history?" - the latter question is often closer to what to what people actually want to know and is more likely to get a good answer from an expert. If you intend to ask the 'What importance do scholars assign to event X' question instead, let us know and we'll remove this question.
Thank you!