At last, after eight grueling years and 73 episodes marked by lavish slaughter (200,000 people dead) and sex, "Game of Thrones" aired its final episode Sunday.

Needless to say, some upset fans were so let down by episode 73 (or Season 8, Episode 6) they're demanding it be remade into something more satisfying.

Despite these grumblings, 19.3 million people tuned-in to HBO to watch the final episode, a record-breaking number for an appointment TV program. Broken down, 13.6 million viewers watched the series finale on the live HBO channel. HBO said prelim viewership numbers from streaming (HBO Now) and on-demand re-watches boosted the total to more than 19.3 million viewers.

Without doubt, episode 73 was the most watched episode of any HBO show, while the 19.3 million viewers is a record for both GoT and HBO overall.

"Game of Thrones" season finale episodes have broken HBO’s overall viewership record since season 5. In particular, the final season of HBO’s adaptation of George R. R. Martin’s “A Song of Ice and Fire” had fantastic viewership in its final season.

Each episode (except one) exceeded viewership from the finale of season 7, which was the series’ best prior to season 8.

And herein lies the rub. With the end of such a fantastic series, HBO now expects a drop in its viewership to more mundane levels.

From previous and bitter experience, HBO has learned that subscribers to its streaming service are more likely to cancel once a program ends compared to viewers of other platforms. The expected cancellations might be boosted by the general feeling among some fans the final episode did them a disservice.

"We're extremely confident that they'll see an uptick in cancellations because they have such high content-oriented consumers," said Buddy Lo, analyst at market research firm Mintel.

HBO is also expensive. At $14.99 per month, HBO Now (the company’s subscription video on demand service) is one of the most expensive streaming platforms. Past research has shown most households don’t want to pay more than about $20 per month for streaming services.

The final episode was an unsatisfying end to a program otherwise marked by brilliant acting and writing and awards galore, which could add to reasons of subcription cancellations.

Game of Thrones Sansa Dany
Sophie Turner (left) and Emilia Clarke posted goodbyes ahead of the "Game of Thrones" finale. Helen Sloan/HBO

[Spoliers ahead] Episode 73 can basically be summed-up by one unmistakable conclusion: Daenerys Targaryen was well and truly mad. Viewers first had a hint of Daenerys' budding psychosis in Season 1 when Daenerys murdered her husband, Khal Drogo (Jason Momoa), by smothering him to death with a pillow.

Her excuse that time: prevent Drogo's wounds from reducing this ailing and once-formidable man into a catatonic vegetable. Fast forward to episode 73 on Sunday, and a raving mad Daenerys justifying Drogon's fiery destruction of King's Landing, and the hundreds of innocent people in it, by declaring this massacre part of her new crusade to cleanse the world of the unclean.

“The finale wrapped a few elements up a tad too cleanly, perhaps going against the show’s original ‘good people don’t triumph’ edicts, but were you truly going to be happy with a defiant Dany standing over the charred bodies of everyone else, ruling a ruined realm?” wrote James White of Empire Magazine.

“It’s not the end everyone would have wanted. It was never going to be.”