Why does Civilization VII freeze for seconds during late-game turns?

I couldn't stand it anymore; in the late game, the CPU would take forever to calculate turns, freezing the screen for seconds. I tried disabling all power-saving options in the BIOS, but the temperature just rose by 5℃ while the lagging remained, which was so frustrating. I used the GamePP Resource Scheduler to max out the I/O priority and cleared 15GB of system fragment cache. RTSS showed peak turn latency dropped from 120ms to 40ms, with core temperatures stabilizing at 72-78℃ per Hardware Sensor.