Missa L'homme armé

Why did composers use the L'homme armé melody for sacred music? Was it simply an excellent cantus firmus, or a challenge handed down from generation to generation of composers? From the translation attached, one can see that the poem invokes the imagery of warfare; the armed man might refer specifically to the mounted soldier.
One scholar has suggested that the development of the early cyclic mass related to the need of the Church to unite following the Great Schism of the 14th century (G. Chew). The image of the "Church Militant" defending Europe against the onslaught of the Turks (Constantinople fell in 1453) might be the reason for the sustained popularity of this "military" mass among composers employed by royal and papal patrons.
Missa L'homme armé