That's not really enormous. It's big compared to most buildings, but ~1million sq ft of retail space is just about the minimum viable mall today. People aren't

That's not really enormous. It's big compared to most buildings, but ~1million sq ft of retail space is just about the minimum viable mall today. People aren't going to the mall to fulfill a specific need, they're going for the variety. It's hard to cram enough variety into much less space than that. For context, Valley Fair, Westfield's mall in San Jose, has 2.2million sq ft, and looking through their list of holdings, it doesn't look like they operate any malls smaller than a million sq ft in North America.