I had the same issue as you did and completed the same steps as you did, I reinstalled the entire game twice deleted all folders etc.
Then, I decided to have a look in the modules folder and what did I see...MODLIB folder was there for some odd reason. I deleted that folder and the game worked from steam, loading the usual launcher.
Even if you think your modules folder is clean go and look there again as something in there may have stayed after reinstalling.
EDIT: Now the game wont launch from the launcher lol. More issues.