I downloaded the offline installer, but when it runs, it just extracts a bunch of files as if it was a zip file. Dled it 2x and transferred it to that computer, same issue.

It is a bit difficult to pinpoint your problem... have you checked that the installer has not been damaged (is it roughly the same size as the gog page says - you mention downloading it twice, but there still might have been something wrong)? What OS are you using? What files are getting extracted and where?

And just to be absolutely sure: Could what you have seen just be the standard gog installation? What I mean is: Have you installed a gog game before? If not, maybe the game did get installed correctly and it just looked weird to you (if that is not the case, I apologize, but sometimes people seem to have certain expectations about how an installer should look and I don't know what you know...)

In any case a screenshot or something similar might be helpful, as I could not reproduce your problem with my offline installer.