The audience grew every season, without exception

Television shows do not usually do this. Audiences peak somewhere in the middle and drift down, and networks accept it as the cost of a long run. Game of Thrones never had a down year. Average first-run US viewers went 2.52, 3.80, 4.97, 6.85, 6.88, 7.69, 10.26, 11.99 million across the eight seasons — the only near-flat step is between seasons four and five, and even that is a small rise rather than a fall. Two things drove it. The first is that HBO let the show build: season one was a modest performer by the standards of what came later, and it was renewed on the strength of critical response and DVD sales rather than overnight ratings. The second is that the show's biggest shocks were designed to be discussed the next morning, which turned each season's ninth episode into an event that pulled in people who were not watching weekly. By the final season the series finale drew 19.3 million people across HBO's platforms — the most-watched episode in the network's history.