it was allowed because britain and france did not want to fight germany essentially, so they let them get on with it until they invaded poland. short of declaring war the allies could do nothing but protest a bit. the sudetenland was part of czechoslovakia, but it had a large population of ethnic germans.orgot to put why. Hitler included austria into germany as part of the anschluss. He did this ebcause he was actually austrian, and wanted to incorporate his hometown into germany. dellick17 · 7 years ago.