After choosing the allegedly harmless exchange variation against the French, he proceeds to start a kingside attack. The key moment comes at move 14, when he cuts off his own QB with the move 14.f4. Black reacts logically, and 16...Qb6 would have given him excellent counterplay. Objectively, Carlsen's play should be criticised as excessively risky, but the fact is that Vallejo's eyes were fixed entirely on kingside defence. As time-trouble approached, he collapsed and lost to a direct attack, with limited material.
Like a number of Lasker's games, one can analyse this effort and say that Magnus was a bit lucky. His play in the opening and early midddlegame was objectively rather dangerous and could have landed him in some trouble. Yet, just as with Lasker, it didn't. Maybe he knew his opponent and knew exactly how far he could go, to unbalance the game enough to create the conditions to outplay him and win?