Question CPU usage is locked at around 50% when using dedicated GPU but never locked when using integrated GPU

Oct 2, 2020
Alright, so here's my spec

Acer E5 475G
Intel core i5 7200u 2.5 ghz
Intel HD 620 integrated gpu
Nvidia 940mx
8GB ddr4 ram

I was playing some game with my laptop that I didn't use for gaming for like 6 months or so (I get back playing games after I quit playing it). I noticed that when I first started the game, it was at nice and steady 60fps, but then in the next 5 seconds it dropped to 20fps, it doesn't even got heated up. Then I checked the usage with Task Manager and realized that it only uses 50% of CPU and 100% of GPU. Then I started the game again with Intel HD (I was using 940mx before) and yes, it doesn't get better, but I noticed that this time, CPU usage is more than 70% now. I've searched a bit that using integrated GPU doesn't really affect CPU usage.

Is something wrong? Do you guys have any idea what happened?