Yeah, I doubt it had much to do with concerns over another's control of their product. They have no concerns with releasing on consoles after all.
They wanted 100% of the revenue which may have made sense based on their projections when they built it 3+ years ago, but then the following things happened:
All of the above lead to a potential miscalculation of both how many users they would have on Origin and how many users they would forego on Steam by being exclusive.
- Simcity flopped
- Star Wars: TOR basically flopped even as a free-to-play title
- Steam has grown massively
- Steam has increased its lead in features rather than Origin closing the gap
That is what keeps me hopeful that EA will wise up and release their games back onto Steam.
None of those reasons seem to be a game changer in my opinion.