That is a dual core CPU, not great not terrible, barely meets the LFS recommended spec :
Recommended computer requirements:
3 GHz CPU, 1024 MB memory,
3D graphics card with at least 512MB memory.
LFS is mostly CPU dependent due to its physics calculations.
A full multiplayer grid requires a fast CPU more than a fast GPU.
Before starting to dig deeper on the multiple possibilities of the fps drop I would recommend you to download a fresh LFS, install it on a new separate folder,reboot PC, open only LFS after restart and connect to the server where you experienced the issue and report back.
You did not mention if it is a laptop (should be due to CPU family) and your windows version (just type version on windows search bar and open System Information, top 2 rows gives you the OS name and Version)