It is true, that before the Nazis came to power, Germany was regarded as one of the least anti-semitic countries in Europe, especially when compared to France, and even England.
Most of the anti-semitism was imported in from their neighbors to the south, Austria, which of course Hitler came from.
Yep. Pre-WWI Germany was pretty hospitable to Jews, as was Poland. We can be very confident of that because of the number of Jews who went to live there. Given a choice, people tend to move to where they feel welcome and safe, and where they can earn a living.
What changed? After WWI, the Russian Bolshevik Revolution, a communist takeover of Hungary by Bela Kun the 1919 Spartacist Rebellion in Germany -- the German middle class were afraid of a Russian-style takeover resulting in mass murder. Hitler came to power by promising to fight any Communist takeover. Hitler said the Jews were behind Communism, and so it became easy to convince the German people to round them up.