Why was appointing church officials important to henry iv?

Because he was a protestant in a catholic country 
So, in order to access to the throne, he had to convert to the catholics.
That's why the church officials were so important, the people wanted to be sure he became a true catholic
("Pais vaut bien une messe")

Wakanda is home to a lot of Vibranium, one of the strongest metals in the Marvel Universe. To keep it out of the wrong hands, the ancestors isolated themselves. ... If it's advanced technology were to be put into the wrong hands, like the ancestors were worried about, it would be devastating