Apparently because “a large number of parents bought Mall Cop tickets with their kids (rather than simply dropping off)” and “the film played surprisingly well outside of major cities.” That’s according to the La Times. They also go on to quote Jeff Black, Sony Pictures Entertainment VP:
“The other secret weapon was that it did proportionally even better in the middle of America than it did in Los Angeles and New York. There’s an audience that maybe isn’t all involved in the Oscar movies.”
The film was originally developed from a concept by star Kevin James under the watchful eye of Sony exec Doug Belgrad. Belgrad now wants a sequel.