A weird cpu+board bricking case

[coakira]

I have a tongfang rebranded laptop with an i5 4210M and a 4GB GTX 960M. Now the mobo is dead, and CPU appears to be dead too since the new mobo doesn't post if I try using it (but board works fine with a celeron 2950M I bought for testing). 

What I did is leave the laptop turned off for a day, no one touched it and it was disconnected from power. When I came back and turned it on, fans turned on, screen stayed black and it turned off after a few seconds, and it never posted no matter what I did. And what I did a day before it was dead is undervolting the CPU using Intel XTU since it was running pretty hot, I don't remember the exact value (tried different ones though and sticked with the most stable one according to stress test) and I didn't change anything else. I ended up getting a replacement and not bothering anymore to fix it, but I really can't understand this case. I'm aware that software can actually kill the hardware if some values are wrong, but is it possible to ruin almost the whole system by a CPU undervolt? My guess for now is that some other voltages could suddenly increase since I left them on auto, but anyway.