Well...
Czechoslovakia was a made up country specifically designed by Wilson, Lloyd George, and Clemenceau to keep Germany down by carving off the area of Germany where most of its coal was being mined. Doing this transferred such a large a Catholic German population that Wilson was afraid the Socialists would not be able to win elections, so they grabbed the Slovak lands and crammed those people into the new country as well.
People forget the oppressive sanctions Germany accepted from WW I. It’s not strange that they grew up resentful and belicose.
It is strange though that a psychotic little man with a tooth brush mustache came into power and vowing to rid Germany of Jews, but that’s another story.
A little known fact is that when Czechoslovakia was sold-out by the west, Poland also took a bit of the country called Zaolzie under the same excuse of being home of many ethnic Poles.