The book does not say if the angels used to be human! Not all angels used to be human or even used to be any mortal species, but there's not generally understood to be fundamental differences in priorities or outlook between angels that were human and angels that weren't.

After Sarenrae told her followers not to go near the smooth scar left above Rovagug's prison, they either misunderstood her or decided to ignore her, and went to build a city there. Rovagug was able to influence the city and the people in it, and did so, making the people twisted and Evil and working towards his own release. Sarenrae eventually sent Her herald to tell the people they were in terrible peril and needed to leave immediately. They murdered the herald. At that point She smote the city. Her Church generally holds that She didn't have a lot of options, but still regrets and repents of Her decision there. 

Asmodeus generally backs Abadar's work to build cities and civilizations, because humans are capable of more of the kinds of tyranny of interest to Asmodeus when they have social organization more sophisticated than a tiny hunter-gatherer tribe. Abadar trades with Asmodeus, though He does not recommend to His followers that they do so.

The book does not say if the angels used to be human! Not all angels used to be human or even used to be any mortal species, but there's not generally understood to be fundamental differences in priorities or outlook between angels that were human and angels that weren't.

....what counts as really loving a mortal? There's, uh, a rumor Desna and Cayden Cailean fucked when He was human and that's why he succeeded at ascending. Erastil is broadly understood to be a giant humanity fanboy who does things like attempt to have a gender on purpose because humans do it and attempting to have a wife on purpose because humans do it and attempting to conceive children on purpose because humans do it. 

After Sarenrae told her followers not to go near the smooth scar left above Rovagug's prison, they either misunderstood her or decided to ignore her, and went to build a city there. Rovagug was able to influence the city and the people in it, and did so, making the people twisted and Evil and working towards his own release. Sarenrae eventually sent Her herald to tell the people they were in terrible peril and needed to leave immediately. They murdered the herald. At that point She smote the city. Her Church generally holds that She didn't have a lot of options, but still regrets and repents of Her decision there. 

Asmodeus generally backs Abadar's work to build cities and civilizations, because humans are capable of more of the kinds of tyranny of interest to Asmodeus when they have social organization more sophisticated than a tiny hunter-gatherer tribe. Abadar trades with Asmodeus, though He does not recommend to His followers that they do so.