Why is map loading so slow in Ghost of Tsushima DIRECTOR'S CUT?

I felt frustrated when loading times in Ghost of Tsushima DIRECTOR'S CUT jumped from 5s to 15s on my Zotac RTX 5070 Ti 16GB XGaming. I tried restarting the game, but the lag came back after 30 minutes. Then I used GamePP Hardware Sensor to check the VRAM state. It was fragmented. I used GamePP System Backup & Config Export to clean it. 3DMark benchmarks showed the load time dropped to 4s. The GPU temperature stayed stable at 65-70℃. It finally feels like a proper game again.