Having lived through the peak of the US Mall years, I blame the downfall on... Nintendo.
The mall was a social center for teens. A lot of money got pumped into the malls from that age group.
Teen boys would go for the arcade. Teen girls would follow, checking out the guys. Many stores catered to that demographic (Spencers, HotTopic, makeup and cheap jewelry stores, etc.)
In short, it was a place to go on casual dates, find dates, hook up, and the like.
My peer group quit going as frequently as we could play SuperMario Brothers for free at home. And, once the internet emerged, that was it... teens rarely leave their houses now, don’t date, and shun all face-to-face contact.
So, in short, Nintendo destroyed the Malls.