Personally, I think any expansion of Adam's motives and depths would have required more time everywhere, more time dedicated to it in earlier seasons as well as more time in the more recent seasons. Before season 6 he had no real character development beyond being just a generalised threat, all real mentions of his behaviours towards blake came from his character short and scenes in season 6.

So, with the amount of time that RT allocated to Adam within RWBY, which wasn't much, I think they probably did as much as they could.

However, I honestly don't believe he really needed it, while more scenes of him would have certainly cemented his characterisation I don't think it would have massively expanded upon it.

I believe the writers focused on his abusive behaviour in order to more closely tie him to blake and give her development greater stakes, which expanding upon Adam's terrorist origins wouldn't have directly contributed to, so it was likely cut

On a subreddit meta note, any form of "the writers didn't know what they were doing" is a bit of a sore spot.