It was always short sighted tax policy. We're just living with the blowback.

But in 1954, apparently intending to stimulate capital investment in manufacturing in order to counter a mild recession, Congress replaced the straight-line approach with "accelerated depreciation," which enabled owners to take huge deductions in the early years of a project’s life. This, Hanchett says, "transformed real-estate development into a lucrative ‘tax shelter.’ An investor making a profit from rental of a new building usually avoided all taxes on that income, since the ‘loss’ from depreciation canceled it out. And when the depreciation exceeded profits from the building itself—as it virtually always did in early years—the investor could use the excess ‘loss’ to cut other income taxes." With realestate values going up during the 1950s and ’60s, savvy investors "could build a structure, claim ‘losses’ for several years while enjoying tax-free income, then sell the project for more than they had originally invested."

Since the "accelerated depreciation" rule did not apply to renovation of existing buildings, investors "now looked away from established downtowns, where vacant land was scarce and new construction difficult," Hanchett says. "Instead, they rushed to put their money into projects at the suburban fringe—especially into shopping centers.

http://archive.wilsonquarterly.com/in-essence/why-america-got-malled