well actually SirBombastic, the knights hospitaller started and were funded by the pope. Its only much later they came to occupy Malta.
First they were started by the pope, then they occupied territory in the holy land, then they came to control the ancient byzantine city of antioch, then they got pushed out of there and came to occupy Cyprus, they left there and became the lords of Rhodes, and only after they were driven out of there did they come to occupy Malta.
In the early 1200's, the time period this mod is set in, the knights hospitaller are just starting out, they're in their infancy, and they started out under the pope who commissioned them and funded them so it makes the most sense to have them as troops for the papacy.