Not being critical of the shot. I would have taken the same shot as well, but I think you drifted slightly off target as the shot broke. This is the last frame of imagery I could get from the video before the shot broke.
Assuming you are spot on at this distance, my guess is that you hit below the brain case and the impact of the bullet on the maxilla or mandible wasn't enough to jar the brain enough for the hog to go down and stay down immediately. He may have died of a brain bleed or brain damage (post trauma swelling) sometime later, as in minutes or hours later.