Same issue here (note: I have same issue in another game too Star Citizen)
RTX 3080
Ryzen 3900X
32GB 3200 (2x16)
1TB m.2 FireCuda - NVMe
Windows 10 - 2004 (Build 21277.1000)
1607994800
I have found a solution and now GPU usage go to 100%
If you're using iCUE (from Corsair), set the PSU to...