Years ago there was a series on TV, THE WORLD AT WAR about WW II.
In the 1980s they added several new episodes in which it was claimed Hitler wanted to expel the Jews to Madagascar, but was blocked because England still controlled the Suez Canal.
So then came the ideas of gas chambers and ovens.
THE WORLD AT WAR - great series
Actually the concentration camps came about because of the problem of what to do with the bodies. The Nazis were already exterminating Jews; the camps industrialized the process.