Well, maybe if you looked into the way the show is produced you'd understand the NBC ratings hardly matter. This is NOT an American show, despite overwhelming American involvement. It doesn't matter if it tanks and NBC doesn't pick it up there WILL be a minimum of 3 thirteen episode seasons we will all have access to. After that, if the show is a hit than we'll probably get a total of 7 seasons......They creative team, the talent, and the finances are all in place and everyone went into the show with the understanding that they will be shooting 39 episodes (three, thirteen episode seasons): Season 1: Hannibal meets Will; Season 2: Hannibal loses Will; Season 3: Hannibal and Will clash. with a 4th season (a re-telling of Red Dragon) also planned.
If he were allowed to go on after that Fuller would like to do: season 5: SOTL; Season 6: Hannibal; Season 7: An as-yet unwritten conclusion.