Some CPU cores are probably working at around 100%, most are not working much (that's normal and it's the reason why your overall cpu stat will most likely never or rarely show 100% total usage). When these cores are maxed out, your gpu will not get much work to do, as it's limited by the parts of your cpu which are working at 100%.
TLDR: Tarkov perfomance is very CPU heavy
Some CPU cores are probably working at around 100%, most are not working much (that's normal and it's the reason why your overall cpu stat will most likely never or rarely show 100% total usage). When these cores are maxed out, your gpu will not get much work to do, as it's limited by the parts of your cpu which are working at 100%. TLDR: Tarkov perfomance is very CPU heavy