It's certainly a pollution issue. Smog concentrates in the LA basin due to the geography and weather, but smog is caused by pollution. It's not the same as fog.Look dude, LA looks like that even today. It's a weather phenomenon, not from pollution.
The data shows that big cities like LA are cleaner today than they were in the past, and it's clear that's due to environmental regulations including cleaner cars.
Look, I don't like regulation, I find it deeply frustrating many times, but I'm not going to say it's all bad. That's just silly.