Why does my PC reboot during large magic explosions in Warhammer III?

During a massive positional battle, my screen suddenly went black and the system rebooted right as a magic explosion hit. I was devastated. I first tried limiting the GPU max power to 80% via software, but my FPS plummeted from 75 to 52, which was a total joke. I then used the GamePP Power Plan Switcher to set the system to Ultimate Performance and enabled LLC in the BIOS. Voltage fluctuation narrowed from 0.4V to 0.1V per GamePP voltage log, and the PSU stayed at 45-52℃ per AIDA64. No more crashes, just pure war.