Also, in this particular case, being a Kask helmet, it stayed in place because it was secured on the rider's head, not just on the brow. There is a piece in the back of every Kask helmet that locks in place, securing the helmet to the occipital bones, which is very important. This ensures the helmet encapsulates the skull, rather than just sitting on a pile of hair.
When the helmet is secured in the back, it is ready to do its job in the event of an impact. If it is not secured, the helmet can come forward and compromise the face, which has happened to some riders. To prevent this, it is important to ensure the helmet is certified to the highest safety level and fits properly in the back. All of the helmet brands that Malvern Saddlery represent have similar retention systems to ensure safety.