Don't get me wrong, bulldozing and rebuilding for the sake of bulldozing and rebuilding is wasteful, even if it is good for the economy at large.
My question begins with - why did they all leave? Why is the new location so much better?
In the case of Omaha, when a shop leaves one mall for another mall, it's because the new mall is in a much more affluent neighborhood, i.e. the hope for more revenue. It's likely that the location will wither and die, and never be rebuilt.
We rarely see something where businesses move out, the building is razed, something new in its place with new tenants. Typically if this happens, it happens because the area has become more prosperous and a new building will attract more customers, so out with the old and in with the new to make even more money.
So as was previously mentioned, those dead malls (we have two of them). One turned into office space. The second one is mostly empty and has been for around 10 years now. This mostly empty mall could be turned into apartments.