Because I have, and the book makes it abundantly clear that "banal" is the perfect word to describe Adolf Eichmann. I don't understand where the Rosenbaum's !!!RAGE!!! at the very concept comes from.

Yes, and a couple of points that Arendt makes in Origins of Totalitarianism were novel and hard to gainsay.

One, that the concentration camp is the central institution of a totalitarian society, a point re-made by Alexander Solzhenitsyn.

And two, that analysis along psychological lines is utterly incompetent to understand the behavior of particularly the keepers but also in some ways the kept in the latter stages of the system. For instance, in the early stages of the Holocaust, the SA were in charge. Being a coterie of thugs, perverts, sexual predators, sadists, and the like, their behavior was evil and deplorable but understandable. The later depredations of the SS don't follow any such paradigm, or any other knowable one. In a totally bankrupt economy, Germany was expending millions of marks building rail cars and railroads, cutting timber and making lumber for the construction of camps, even when the Nazis knew they were finished and should have been cutting and running for self-protection.

And in the Soviet Union, Stalin's dispossession of the Ukrainian kulaks was regrettable and devastating, but he wanted no pretenders of any kind to any kind of political or economic power, which the kulaks were demonstrating. As a result, Soviet agriculture never recovered, but Stalin was willing to take the chance. Even the leadership purges of the late thirties follow a similar model. But after Stalin had died, the gulag system continued under its own steam. Khrushchev, Brezhnev, even Gorbachev were unable to put a stop to it. It had a life of its own.