Battlefield 1943 producer Patrick Liu explained the studio's unique design philosophy while making the game, which boiled down to "make the game as long as resources last." They maximized the amount of content they produced under this strategy by settling on the somewhat smaller scope of the game early, and focusing on recreating the Battlefield experience to adhere to that scope.
Some decisions made under this philosophy include making ammunition and health auto-regenerate, cutting down on tiresome resource runs back to your home base. This decision led to others, including the removal of the medic and engineer classes. It also let them focus on perfecting a handful of maps and gametypes, which, while iterated from previous installments in the franchise, also saw major adjustments in 1943.
The result was a project developed by 15 series veterans at once, at one-tenth of the cost of a full DICE game, which broke day one, week one and month one downloadable sales records. It's no surprise that Liu expressed interest in developing more "games of this size and scope" -- when handled correctly, it sounds like a miniature entry in a major franchise can be quite the profitable cash cow.