"...negotiating with a certain dictator in Germany...."

You mean why did it  go "so wrong" for you, but certainly not for me and Catholics I know. The tragedy is that the Reich-Vatican concordat and the earlier concordat with the Weimar Republic and the concordats with Bavaria, Prussia and Baden didn't stop National Socialist attacks on the CC during the 1930's, especially after Pius XI's encyclical MIT BRENNENDER SORGE -- which only triggered the Nazi state to levy accusations and charges against priests and increase their arrest throughout Germany. All the concordat asked was that the state give the CC the right to fulfill its mission to proclaim the Gospel and administer the sacraments, which was giving to God, God's due, the worship due to Him through Catholic practice.