joelong_1998 BF1 utilizes the CPU highly, therefore your somewhat lowered GPU utilization and FPS, with your CPU and GPU, would normally make sense. In certain games the i5-4570 is a sufficiently powerful match to the GTX 1070, but in BF1 @ 1080p with a GTX 1070, might fall short.
However, the utilization falling to 30 FPS doesn't sound right to me. I believe the i5-4570 thermal throttles at just below 73C. Even though your average CPU core temps range from 65C - 67C, your max is 77C. I wonder if your game play is normal until the temps push just 3 or 4 degrees above 72.72°C max operating temperature and then CPU thermal throttles itself (down clocks itself as a safety response to excess heat detected).
FYI: I'm assuming that the 30 FPS is during actual game play and not a cut scene.
Please try the following: Instead of using MSI afterburner, please download HWMonitor to check CPU temps / CPU utilization & GPU utilization. I'm guessing that when the CPU temps achieve 73C the CPU downclocks, which means the CPU can no longer keeps up with the GPU, and you see lower GPU utilization and game play FPS:
https://www.cpuid.com/downloads/hwmonitor/hwmonitor_1.32.exe
The next thing I'd like you to do is open up your computer case, and turn it on it's side while the power is on. The motherboard should be facing up toward the ceiling. Grab a floor or desk fan from your home, turn it on and point it toward the motherboard. Now play BF1 for five minutes and read the CPU temp, CPU utilization and GPU utilization, and FPS counter (via origin). Any change? Please report your findings back here.