I mean, to be fair, 78725 is effectively the middle of nowhere in Austin. It makes sense if Musk's goal was to choose a fairly undeveloped exurb, but the gigafactory is as close to Manor and Webberville as it is to central Austin.
I know Fremont is suburban, but it's a well incorporated suburb to both SF, Oakland and San Jose. 78725 is on the opposite side of Austin from most of the fancy neighborhoods.