The facts and the timeline on this have been sort of murky, but I believe Ridley said they looked at the video before he finished and didn't find anything wrong with the drop, so they didn't talk to him about it. I believe Tiger said yesterday the first time they talked to him was yesterday (Saturday) morning.
And it isn't cheating per se. I don't think anyone said he was "cheating" when he dropped that ball. But he knows that in his pissed off state he conflated two of the different drop options and took an illegal drop. He also admitted he was trying to gain an advantage from it.
The obvious bad precedent this sets is that you can break rules out there and if you aren't caught you get away with it. If you are caught, oh well, they just add the strokes later. That's one reason the penalty was so harsh before, to absolutely discourage it.
Guess it's just a new era, one probably driven like bb said by ratings. You wonder if this had been, say, Jon Senden if the decision would've been the same.