After all, a medium was just a medium, and the demon lords felt that it was like gearing a suit or something.
How could they rely on their suit to fight the enemies?
That's an embarrassment for the demon lords!
Asmodeus didn't think that letting Ainsley fight the archangel was a bad thing.
Since Ainsley was the one who said that she wanted to try, then why not?
Atherton and Father Dracu also occasionally switch control with their demon lords to do some secret actions, cooperating seamlessly with the demon lords instead of just becoming a 'robot'.
Asmodeus didn't want to debate with these chibi demon lords who always looked down on him just because his strength relied on lust.
[Anyway, the little kid said she wanted to try, and this lord will listen to her and let her try. End of story.]