Flying drones is still legal in most jurisdictions. It doesn't excuse it, of course, but in most instances this was not illegal behavior.
In terms of competitive edge, I'd think any information gained would be less than the edge gained from leaking your opponents' hotel, or allowing your fans to throw piss with impunity, turning the sprinklers on during your walkthrough, or countless other indignities suffered in CONCACAF. It's not quite like telling the batter what pitch is coming.
Of course they shouldn't have done it. Besides the ethical reasons. the risk/reward calculus is so unfavorable.