Momentum, driven by old franchises/licenses (Sims, Madden, etc), plus volume, AKA: the shotgun approach.
Make 30 sequels of last year(s') hits and bank on a few of them being wildly successful. Repeat again next year based on whatever worked last year. Repeat ad nauseum.
Their strategy has no longevity to it, but it's working right now because consumers are very stupid and more than happy to piss their money away on whatever is "popular" (often artificially) and easily recognizable.