They were meant to be episodic, in a way, which means chorus recaps and the like.

This reminds me that the few times I've seen historians earnestly talk about all the "lost epics" of the expanded Iliad poetic universe have been very funny, because at their bluntest they're just sort of hemming and hawing around a point that's basically "so it was all just a big fanfic scene, really, and a lot of it was bad, and it represented a bunch of different contradictory canons, and like every character no one even liked got a spinoff epic about them getting lunch that one time... So really it seems the two books we do have seem to be what were considered the best, and certainly were the most popular of all them which is why any copies survived at all."

Like obviously they'd still be really neat to have, but it's really funny to think about how this big chunk of what's held up as one of the pillars of western literary culture was just like, the contemporary equivalent of a fanfic scene where everyone involved was just kind of making up their own stories about these mythic characters and some of it was popular enough to get repeated down the line and only two stories were popular enough to still be getting copied many centuries later.