The targeting penalty is essentially for attacking the head of the opposing player. This actually doesn't have to be helmet the helmet as a shoulder thrown into a defenseless player's head can also be called, but targeting is often "helmet to helmet" when the defender goes in with the top of his helmet into the head of the offensive player.
In this case, the defender put his left shoulder into the chest of the player to make a completely legal (albeit very hard) hit, and their heads knocked into each other in response. The defender did not lead with his head nor did he make the initial hit on the offensive player's head. When the contact happened it was the side of both player's helmets hitting in a way that, unfortunately, cause a concussion to the BYU player. Nothing about the play suggests the Kansas player was going after the BYU player's head. Also, the hit happened after the Kansas player busted through a blocker and was standing upright so it's not as though the Kansas player even had any time to react or adjust much before impact.
Opposing players (O-line and D-linemen in particular) will often hit their helmets together as part of incidental contact to blocking and tackling in the ordinary course as part of any given play and none of that is targeting. Again, it's not about merely making contact, but, as the name implies, targeting the player's head.