Why does Human Host lag when facing large fortresses?

I was so excited to finish my grand fortress, but the frame rate instantly tanked from 120 to 45, which was maddening. I tried manually setting the priority in Task Manager, but the game just crashed, proving that crude intervention doesn't work. I then used the GamePP Resource Scheduler to set the main process to real-time priority and applied core binding. Frame generation time converged to 11-14ms per RTSS, and GPU temperatures stayed at 65-72℃ per MSI Afterburner, compared to the previous 15-45ms per RTSS.