It wasn't a failed slider. Larson said that he went in to try and get next to him to kill his momentum and when he realized it wasn't going to stick he knew he had to hit him to bog him down. If Larson lifts there his momentum is killed and KB is gone. He pulled a banzai move and it didn't stick. KB even said that he expected a slider and when Larson didn't give it to him he was shocked. He said it's the first time he expected a slider, prepared for a slider and then it didn't happen. KB talked about how he lifted a little to prepare to cut back down on a cross over attempt, but Larson didn't want him to have the opportunity to do it so he hit him. It was a series of calculated moves by both guys, which is amazing that at the speed they were traveling they are capable to process like that and change plans on a whim. It was a fantastic display of what we all wish it was like all the time. End of the day two of the absolute best, if not the two best wheel man the sport has to offer put on a great display of technical and brute skill in those cars.