As a former god, he is someone who reached the apex of transformation whose mind and soul were even at risk of transforming into those of the progenitor. So his existence is closest in form and spirit to that of the progenitor.
The next best level of existence closest to the form and spirit of the progenitor after the existence of the god of the pathway is the angels of the pathway. This is why they are the best candidates for gods of their pathways to possess.
A god of a pathway will find it very easy to possess an angel of their pathway because they have nearly identical physiques and many divine abilities in common. They will have the same divine beast form.
The opposite will be the case for the gods of other pathways, as the angels of other pathways will be the most different in physique. Only special gods like the god of dreams, who can overwrite the mind, can bypass the restriction of the differences in body and divine abilities.
