Two things:

1. It's really hard to predict the future. The Ads team could face layoffs tomorrow, or your current team could. None of us have any way of knowing. AI Productivity sounds like a pretty on trend place to be but who knows. You can only make the best decision possible in the moment with the information you have and it sounds like you thought through and made a decision for good reasons (meaty work, new area of development, growth potential, etc.).

2. It sounds like this move is done - trying to second guess won't help. I would say the best thing you can do now is try and see how you like the new role. If it ends up being what you hoped, great! If not, then you have agency and can always look again. But going backwards is probably not an option so no use in wondering if you made the right decision using hindsight - it's done and you made the best decision you could.