The reason for Hannibal's success can also be cited as the reason for its cancellation. The series was too artsy, too gory, too esoteric, too niche. The viewership for Hannibal was always small, smart and dedicated.
The show was produced by Bryan Fuller, responsible for such cult TV series' as Heroes (being revived and revised this fall on NBC), Wonderfalls, Dead Like Me, and Pushing Daisies. These series' were odd and macabre, balancing malaise with humor and death with dead-pan that made them critical hits and viewer delights for those cool and hip enough to catch on to their unique comic gifts. However, they never broke wide enough to get anything beyond a third season renewal. The sole exception being Heroes, which played for four seasons on NBC.
The acting on them was always above average. On Hannibal it was almost always very good, sometimes exceptional. The Hugh Dancy (even though a classically trained British actor) portrayed protagonist, the American born Will Graham, lived on the edge of madness and hysteria because his unique method for catching killers was method. Graham could visualize their inner well being, emotional and mental states to the nth detail. Hannibal, played by the brilliant Danish actor Mads Mikkelsen, and who really was the insane one, balanced off Dancy's method with a steely classically trained precision that never broke character. The method of Hannibal's madness was in watching who would go crazy by breaking character first.
The Poster Posse, in their salute to Hannibal, tries to capture that dichotomy in the dominant color palette that the series was shot in: cool and warm tones. I think you will agree that the posters have their own angelic and satanic delights.