Lol @ some of the replies.
"I have this problem because the skin on my hands are either too rough or dry to get traction on the cap. And my finger prints aren't that deep like some people's [ridges] are.
So, he's probably strong enough, but his skin is probablt not quite able to grip the cap well enough."
"His problem is he's so strong that his grip is preventing the cap from spinning. I bet at the end of the video he rips the whole top off."