Unlike Germany, in Croatia RC Church was not in jeopardy and there was no reason for Pius XII to support criminal Ustasha regime who had a goal to exterminate Jews and Orthodox Christians in order to make Croatia 100% Catholic within 10 years.
One may say that Pius XII was unaware of this. Perhaps, although highly unlikely because Ustasha did not hide their intentions.
One may say that RC Chrurch was not involved in Nazi crimes. True for Western Europe, wrong for Croatia.
Croatian officials and Ustasa militia view a group of children in the care of nuns at the Jastrebarsko concentration camp. [Photograph #46612]USHMM
The result of "care can be seen in USHMM photo archive
Under Canon law of RC Church, clergy can not work outside of Church without having tacit Church approval.
In this case, assigned work was to run Concentration camp and exterminate Orthodox Christian children.
What happened after Hitler's demise is equally distrubing. Vatican spirited Nazi war criminals to South America to escape justice.
And documents show that Pius XII personally intervened with Argentina government on Ustasha Nazi behalf.
After the horrendous crimes of RC clergy against Orthodox Christians became known, what was the reaction of Pius XII? EHe elevated Archbishop Stepinac, head of RC Church in Croatia during Nazi regime to the Cardinal.
Pius XII was not a Hitler's Pope, but he was a Nazi supporter who aided and abetted Nazi war crimes, helped perpetrators escape justice, and helped Nazi loot find a safe place in Vatican.