Why does my PCCOOLER RZ820 throttle in Civilization VII late game?

I was desperate when Civ VII turns took 15 seconds instead of 2. I tried maxing the fan to 2000 RPM, but the noise was unbearable and temps only dropped 3C. I switched to GamePP Fan Curve Configuration, setting 70C to 1500 RPM and 80C to 100% speed. AIDA64 confirmed temps stabilized at 78-82C and frequency held at 5.0-5.2GHz. This setup saves my sanity and performance.