It might be partly intentional, but not in a big conspiratorial sense of it being actively suppressed by a shadowy cabal, but more in a self-regulating "I shouldn't bring this up since it would provoke a bunch of other questions which I don't want to answer" sense. In the liberal mind, without any material analysis, the Nazis are a unique evil... except a ton of the stuff they did was also done (perhaps in a lesser form and scale, but still) by the countries which fought them. The persecution of leftists is obviously going to be ignored, since the US and its various client states and countries they couped did a whole ton of that. The genocide of the Romani is going to be ignored by a lot of Europeans, since they'd have to face that their beliefs and rhetoric about Roma people sure don't seem that far off from what a Nazi would say.

There's also another aspect of this, which is with the broader slaughter perpetrated by the Nazis. In the popular consciousness, the Nazis are primarily linked with concentration camps and gas chambers, which ignores all the people who died a simpler death - just shot by the SS and dumped in a ditch, or killed by bombardment. That also has to be ignored, since acknowledging it brings up some broader questions about war - you'd start having to ask questions about how the US bombing the shit out of Korea and Vietnam is perfectly legitimate "war" and not in any way genocidal (I mean, the bombers weren't specifically targeting Korean people... they were just bombing cities in a country which happened to be populated by Koreans), or how having US troops go village to village in Vietnam looking for Vietcong and doing a ton of massacres is different from just having Einsatzgruppen.

So, stuff gets ignored or has attention drawn away from it in popular media and propaganda, and that trickles down to the common person, who's not going to go out and read a book on their own, and so gets a twisted, ahistorical understanding of what happened.