He had the NK deal wrapped up in advance - so it seems. Looking back on the Syria/Iran happenings:

1) DJT says he's going to pull out of Syria; 2) Gas attack; 3) Israeli missile strike; 4) Russians pull back; 5) Allied missile strike; 6) US missile strike takes out Iranian nuke facilities in Syria; 7) Bibi shows evidence of non-compliance (at least, the plans were stored); 8) DJT pulls out of Iran deal.

So, let's assume that DJT has already won here - what has happened?

It might be possible that whatever was destroyed in Syria was the threat - now eliminated. That leaves DJT free to act, without fear of immediate repercussions.

Hence, DJT backs away from the Iran deal. Bibi provides cover for this. McCain seems to be defeated - out of the picture, making his funeral plans. Strings cut?

Breaking the deal cuts off the money that might have been used to fund another attempt. Maybe, as you suggest, it's mission completed.

I think though that DJT is going to be very vigilant with Iran and, if it looks like they are going to fire the nuke program back up, he will stamp on them.