Just a theory...
Not saying you have a Cummins spinner there, but here's my experience with aluminum spinners...
We use Cummins aluminum spinners on our Jabiru LSAs. Been using them since 2008 or so... probably close to 80 airplanes, plus Arion Lightnings. I've seen very few cracks, and the ones I have seen were small and attributed to over-tightening of the screws. I haven't seen anything catastrophic like the OP's picture. Of course, we fly with less horsepower and fewer Gs as well.
The reflection on the spinner in the OP's photo indicates a depression around the screws, which makes it appear that the screws are too tight. We recommend our customers to tighten them down just until snug with a hand screwdriver-- just until the plastic washers begin to compress, and almost zero distortion in the reflection around the screw.
Also, our cones and backplates are match drilled as a finished set at Cummins. If the Van's backplate has a slightly different angle to the flange than the spinner cone and you tighten it down that much, I could see it forming a stress riser and cracking over time--especially with the large distance between the prop cutout and the torn hole, which probably allowed the edge portion to vibrate excessively. But the spinner manufacturer would have more data about that.