How to fix CPU drop in games on macbook?

Question

macbook

Installed Windows 10 Pro via Bootcamp, updated all drivers, set up the system. Downloaded GTA 5 and went to play. At first, I kept a stable 70-80 fps at medium-high, but after 5-10 minutes the processor began to go into throttling, although the percentage did not even warm up to 80 degrees. Put ThrottleStop, disabled TurboBoost on the advice from the Internet. The frequency began to stay even, never dipped from 2300. All the same, the first 5-10 minutes the game goes at a stable 70-80 frames, but after that the load on the processor starts to drop from 20-30% to 5-10%, the FPS drops accordingly to 20-30 frames. The processor and video card still do not heat up above 80-85 degrees. I thought that the problem was bottlenecking, but it works according to a different principle, my video card is much weaker than the processor, and he calmly opens it. After I thought about overheating, but after all, in the first 5-10 minutes, when the game produces 70-80 frames, the processor and video card have exactly the same temperature as at 20-30 fps. I read on some forum that FPS can drop due to overheating of the SSD, but it also keeps an average temperature of 35-40 degrees. The power mode is set to "high performance", the minimum values ​​​​of the processor are set to 100% both from the network and from the battery.

Maybe someone knows what the problem is? This is the first time I've encountered this...

MacBook Pro Retina 16''

i9 9880h 4.30 Ghz

AMD Radeon Pro 5500M 4GB

16 GB Ram