Low gpu and high CPU usage

Platform - PC, Steam
Greetings, I have a laptop with a GTX1650 and i7-9750hf, I played around with the game's configurations and arrived at maximum performance on low settings with normal graphics on 30-45 fps. But even so, my video card is idle, while the processor is 85-95% busy at minimum settings that affect the processor power. 
I decided to test how the Marathon would run on a laptop with an i5-13420H without a graphics card. I was surprised that the game sometimes ran at 60 fps, despite the graphics being terrible (after all, I didn't have a graphics card). So, this request was made to improve the processor optimization.