[He has a hint of fondness to it, much as he can't be that surprised he and Edna didn't exactly get along. As for his questions, Mikleo's approach remains solemn, mostly, he should be the one who's sorry for the tldr, but u asked for it.]
I don't know what the exact reason was. But... Malevolence, it's not evil. Not really. It can build up from the negativity in humans and the world itself, and even us seraphim. A seraph without a vessel or one that resides in vessel that gets corrupted would be easily susceptible to it. Sometimes that means we'd become a hellion.