The connecting cable cannot have done that, thats just not how electricity works. The point of the EPS 12V cable is to provide more grounds and more 12V lines to reduce the current flowing through each line, or to allow more overall current to be drawn, there is also a large set of power regulators between your CPU and the power supply that regulate its power and reduce to voltage down to what it needs. The EPS connector allows the CPU to use more power, but it will still only use as much as it needs. If the voltage settings on the crosshair werent set up properly however then you can blow it out.
What is most likely is that your CPU was either OC'ed and finally gave out, overvoltage and finally died, or it just reached the end of its life and expired with a pop and a black mark.