Several things here.
I'm sorry but his father who manages him and his trainer i.e. Virgil Hunter should have stopped this fight from happening. I know it was probably Amir due to his headstrong ways, but this was the mother of all bad match-ups. It just wasn't possible for Amir to fight a guy who would outweigh by over a stone, and who is one of the hardest punchers in the game. You can't simply move up the lbs ladder and hope to be the same, it does't happen. I've been there (not boxing), moved up and it took time for my power to build again from what is was.
As for the fight. Yes he did move around and stick him, which did confuse Canelo but he knew deep down he would wilt in the later rounds . No one yet has mentioned how tired Amir looked in the fifth round. He was sucking air folks. When the sixth started, his legs were slow, the movement was gone and he was dropping his hands, which is the greatest cardinal error a trainer tells you never to indulge in, and that's when you first walk into the gym, not when you have been a pro for a decade. Amir did take some solid shots from Canelo, and his chin is ok, just not great. But again his body couldn't take the wear and tear and he succumbed as many had feared.
What now for him? I'm sorry to say this but he should seriously think of a few lesser fights and just finish up. The blow he took had a great deal of force behind it and he was out cold for a couple of minutes. Severe concussions like that finish off what punch resistance a boxer has. There are so many examples of this, one being Roy Jones. I don't want to see him slurring his words, just look at Riddick Bowe, James Toney, Tommy Hearns etc, the latter two I have met in person and I was shocked to see their deterioration. That is no way for once proud and powerful men to live.
As for Canelo, I don't blame him for not having fought the Golovkin. He simply has no answer to the fight that triple G will bring to him. Canelo relies on power and forward movement, something which will have him meet the steel willed and fisted Golovkin head-on, which will result in him following what happened to Khan. He can't outbox him, as Golovkin came from an excellent amateur pedigree, a silver medalist olympian, world champion, who shows true ring craft. What has astounded me is the level of punishment he can take. I've seen shots hit him, when he was unaware and he just walked through them. The man is a beast personified. But hey, it will still be good to see the two meet.