Ludendorff, like many of his generation, was operating under the delusional belief that Germany should and could control the entirety of Central Europe.

You can read about the German idea of "Mitteleuropa" at this post: https://www.reddit.com/r/AskHistorians/comments/2x92cm/did_the_german_empire_have_a_similar_treaty_like/coyde4e.

The idea appears not to have been his but to have originated with the author of, you guessed it, "Mtteleuropa," Frederich Naumann.