Alvarez was having success in the opening frame with the legs kicks, really threw McGregor off his groove early. Then he stopped using the leg kicks and got knocked down.
It seems like the same old story in this fight where a shorter guy is fighting a longer guy. Just like with Edgar vs Aldo too; the leg kicks equalize the playing field and they have success with them, but then for some reason when they start getting boxed up they get so hung up on the fact that the guy has a reach advantage that they try to 'prove' they are a 'better' striker by trying to trade hands with the guy who has longer hands? Or because they are thinking so much about the reach, they can only think of doing punching themselves? Smdhtbqhwt onii-fam.
McGregor, like Diaz (or Wonderboy), is very front foot heavy, and the forward lean creates false distance; they are ready to evade and react to any strike, except ones that are below the belt. There is zero reason to not exploit that, you either win out right, or force them to adjust to less familiar tactics, win-win either way.
Trying to fight one of these fighters heads up like that like trying to smack your face into a boulder rolling downhill. McGregor found that in the first Diaz fight (Diaz basically spends all his time doing boxing and jiu-jitsu; every guy who has ever beaten him so far has generally done it by exploiting the holes in his lack of wrestling or kickboxing, rather than smacking their faces into the boulder. Which makes the fact that McGregor managed to take a decision the second time around by basically coming at Diaz head on again a very impressive achievement. Smart game planning? I'd say not really, but sometimes all you have is a hammer, and in his niche he showed that he has a really good hammer [something everyone else needs to game plan around]).