They didn't "build it" as such. The Tesla plant is the old GM/Toyota NUMMI plant which built collaborative Toyota and GM cars and pickups for years, which was in turn a GM-exclusive plant for years before that.
It's an OLD car plant, modernized and updated no doubt by Tesla. But Tesla certainly didn't build all of it. They simply grabbed the otherwise disused NUMMI plant for cheap. There were a LOT of good reasons for doing that, ranging from existing infrastructure dedicated to building cars, to workers from what was one of the world's best car factories, to local suppliers, machines, room to expand, etc. Reusing NUMMI was a great idea for Tesla and everyone else too.
This paint booth problem can and will be solved. It won't be enough to stop Tesla or any other auto maker. It's merely something they need to fix.