Outdated/terrible mesh slap or leaked private mod... From quite a while ago. Definitely isn't going to work on the newest version of the game without issues.
What i mean is, the mod is most probably unfinished and is incompatible with the current version of the game and may break quite a few things. also, using other bootleg websites is pretty risky as you could get viruses/malware etc.
You can't "import" cars from other games to BeamNG, other than from Automation... STmods is a sketchy website, they probably stole this as an unfinished private mod from someone and are lying that they imported it from NFS.