the reasons I started learning about this

The reason I started learning about this, was that some people suggested the Holocaust wasn't necessarily the worst genocide in history, because the term 'genocide' had been narrowly defined to intentionally avoid accountability for the countries who were in power after WW2, especially the crimes committed they during their colonialism efforts.

These suggestions aren't meant to downplay the crimes committed during the Holocaust in any way, but rather to add additional context about other mass crimes that might have been minimized due to "history being written by the victors" (such as King Leopold II's Congo Free State, or the Atlantic slave trade).

More along those lines

Here's some more information, specifically along this more subversive line of thought:

• Imperial boomerang — Those countries that gain experience oppressing people outside their country may eventually start using those techniques to oppress people inside too.