He did rallies in surrounding-ish areas; the majority of the state between the two cities is a lot more conservative, so maybe he just genuinely doesn't know much about the city?
Because if he knew anything about Pittsburgh, he'd know we were a smog-covered hell hole until just a few decades back. We should know the need to go green better than anyone.
My guess is that his rally planners put him in economically-drained former coal towns where they're blaming everything on regulations, and not a single-minded focus on a finite/destructive resource (I see a lot of Trump bumper stickers & signs still up just 45 minutes out of the city, so he has supporters out there). He then remembered hearing about Pittsburgh pre-1975, & presumed places like Moon represent the city.
... Which they don't.