Question City800 UPS 800VA keeps overloading when playing games

Feb 9, 2020
I recently bought a new UPS for safety purposes due to the recent event my PSU was fried while gaming . Both the PSU and the power cords from my monitor was plugged into an extension cord and then a white flash with a blew up sound came from my extension cord and fried my PSU only not the other components I checked it already and everything else was fine . So back to the point, replaced my PSU and bought a brand new UPS to plug both of the monitor and PSU cord to the UPS and it worked fine until I tried playing my games the UPS started beeping indicating an overload and later shuts down the PC .

My specs are
intel core i7 930 Bloomfield
ZOTAC GeForce GTX 950
Cheap 550 watt PSU

All my BIOS settings are at default, I have never touched any of it and literally everything is set AUTO

So here is the question,

1) Why did the other PSU "fried"? The extension cord is not a surge protector obviously, there was no thunderstorm/lightning etc during the time it exploded and when that thing blowed up the only thing that was fried was my PSU not the extension cord nor the cables connecting the PSU to the extension cord or my other components.

2) Why is the UPS gets overload when Im playing games and how do I play games without it being overloaded

3) Assuming the PC is overclocking being the reason why my PSU was fried earlier, I would rather stop the PC from overclocking and just run in stable state and being able to play games without frying anything and can someone please teach me how to stop overcloking.