Canelo froze under the spotlight against Floyd. The pressure got to him, he folded like a wet blanket, he "choked" if you will. It was extreme mental fragility on Canelo's part. It was, quite frankly, embarrassing to watch.
There's different levels of fear, there's Michael Spinks vs Mike Tyson, where he's afraid he's going to die. Then there's a mental block that fighters get where they enter a fight and don't know what they're doing after 4 rounds. At one point, I believe Chepo told Canelo to just "punch him" hoping Canelo would at least be able to do that. He couldn't even do that.