Yeah, they hotfixed that like 5 minutes after launch, and it took a little while for Steam to catch up for everyone.

FactoryGameSteam.exe is definitely correct, probably because they now maintain FactoryGameEpic.exe and maybe a couple others, for the console releases they"re working on. But they seem tobhave neglected to instruct Steam that the exe name had change, so Steam was still looking for FactoryGame.exe. Renaming the file was an effective workaround for the first hour or so.