Fallen angels

It's striking how little the Bible explicitly has to say about the fall of angels. Just a few scattered, sometimes ambiguous passages. 

Liberals say the theology of fallen angels is a Second Temple development (e.g. 1 Enoch). And because it's a later development, this is legendary embellishment or pious fiction. Tacked on at a later date. But there are basic problems with that characterization: 

i) Even in the NT, reference to the fall of angels is scant. Even in the Gospels, Satan isn't classified as a fallen angel. Yet the theological narrative of fallen angels was already in place by then.

ii) Even if we grant liberal dating for the sake of argument, they also tend to date the Pentateuch to the Exilic period, so on their own dating scheme, the fall of angels isn't an especially late development in relation to the OT narrative.

iii) Although Scripture doesn't say much about the fallen of angels, the OT has a lot to say about angels generally, as well as moral evil generally. This goes all the way back to the Pentateuch, including Genesis in particular. So angels and moral evil already figure in the earliest stages of the OT plot. 

It is, however, a short step from the existence of angels in general to evil angels in particular. Likewise, the origin of moral evil is a natural question to ask. Is that confined to the human realm? Or does it have a parallel in the angelic realm? And given the interaction between men and angels in Scripture, it's a short step to the idea that evil angels as well as good angels intersect with human history. So there's no overriding reason to assume this is a late theological development.