It's really surprising to be honest - the card looks so robust as if it could stand a bit of beating. But what do I know.In the OPs case, I am not convinced it is being caused by the lack of the second PCI-e cable...sure, it doesn't help...but, for it to happen when turning the system on for the first time (least I assume it was the first time) meaning the GPU under no load makes me think it really is an inherent weakness somewhere in those cards, whether a capacitor or transistor or something that is prone to breaking on movement.
I recall saying the same thing on another thread yesterday about another GPU failure of some description