The lesson is "If it ain't broke, don't fix it!"
Now that is it broke, I honestly have no idea other than rechecking all connections to make sure they are fully seated because thermal paste shouldn't carry a current.
* I presume you did not remove the CPU or loosen the ZIF socket?
* I presume there is zero effort to boot . . . it is just dead? No PSU fan movement, nor CPU fan movement?
* I presume no LED lights are glowing (other than memOK)?!
* Did you try a single stick of RAM? Followed by another single stick of RAM? I note that is 1.65V RAM. Is the BIOS set to run that? I can't remember but does the i7-2600k support that voltage?
* I presume you grounded yourself before working inside your PC and it was completely unplugged and discharged by holding the power button in for a few seconds before working on the PC?
Besides checking connections (assuming all were fully seated) you can remove the power switch from the MB front I/O header and short the two leads briefly with a flat screwdriver blade. If the PC comes to life then coincident bad switch.
If not then I would unplug the PSU from everything except one or two fans (or connect one or two fans through the Molex connector if not are presently connected) and then short the green wire to any black wire in the 24pin connector ("paperclip test"). The PSU should spring to life until disconnected from the green wire.
Thank you, when I get back to my PC I will try the above.