I mean it find it very hard to believe that your PSU could have done something to your card so bad that it kills it...while also not affecting any other part if your system or killing itself.
It's perhaps a bit undersized for a x80ti-class card, but even then it shouldn't cause any damage.
Card was probably ready to kick the bucket when you bought it.
Also, pretty much every PSU i've ever heard of has 2x 6+2pin PCIE connectors feeding off a single port on your PSU. The fact that both PCIE connectors split off from a single cable isn't unusual in any way.