I watched it for the first time last night ( I wanted to wait to see the highlights package and India's collapse)
There are two objects which fly from the helmet after impact.
One object looked like a thick(ish) sliver, which could well be the brim splitting.
With regard to the safety element, I recall when I rode motorbikes, a while back, being told that if I dropped my helmet it would weaken on the impact area. It is a reasonable assumption that the helmet may be a good age and had a lot of use, hence wear and tear.
Is that the case with the modern materials and construction? What material was his lid made of?