GTX1070 short preventing POST?

I'll preface by saying i've witnessed multiple GPU failures in the past 20 years of pc building and repair, but this might be a new one for me. Typically, if a GPU fails, the system will still power on and POST and you can use onboard video to diagnose a dead GPU. This didn't seem to be the case.

Main System specs:

* Intel i5 6600k + Z170 mobo

* EVGA GTX1070SC ACX3.0

* Corsair CX600M PSU

Thinking that the system not powering on was the result of a PSU failure (and also the plan of building a new rig anyways), i swapped it out with no resolve. Same issue. No power on. I decide to put the 1070 into my new build as was the plan, so now i'm dealing with an X570 motherboard, a CX650M PSU, and an AMD R7-3800x, and again, not getting to POST.

Only after removing the GPU completely and swapping for a 1060 did everything work just fine. The 1070 had been working on the intel setup for the past 3 years. There do not seem to be any fused pins on the PCIE connector of the 1070 (as i would have suspected), i'm just puzzled as to how this card's failure could prevent POST. I'm not necessarily in a rush to buy another $400 graphics card and can use this 1060 for a little while longer (it was planned for my wife's rig that is in the purchasing process).