RPCS3 shut down my monitor

Its definitely not a problem with Your monitor, but with Your hardware (PC).

I guess, Your PC is overheating, or Your graphic card have some problems (overheating, power delivery), or at last its graphic drivers problems (vulkan drivers specifically).

To find out the cause, i would install some monitoring software first, like gpu-z, hwinfo, or anything else and save temp and maybe  voltage values into log. Or use some OSD program to see cpu, gpu temperature on the screen while playing.

Also, just after the blackout, go to Event Viewer (right click on window icon and its on dropdown menu) and navigate to Windows logs (forgot how this menu is in english) and in submenu click System or Application, to see errror logs. Look for the time of occurence and pay attention on red triangle signs. Read carefully content of the error. It gives usually more clues what happened, because it stores errors that appear just right before the freeeze.

For now it was one time. so i'll wait until it will happen again (if it will). and i'll check that out.