Demographic changes. Times are up for the pastime where entire families bum around in malls to enjoy aircon and do 'window shopping'.
Today, people have different hobbies and activities, shopping is down to the purpose of getting what is needed. Malls are no longer the sole source for that.
With the high rental for shops, small niche shops can't survive anyway, so what is left is a boring standard portfolio of brands for goods and food.