Why didn’t people like the end of Game of Thrones?

Note:  this answer contains spoilers for the end of the HBO television series, “Game of Thrones.”  The end of the Game of Thrones television series was a bit divisive among viewers for a number of reasons.  First, some believed that one of the series’ principal and most popular characters, Daenerys Targaryen, had been – if flawed – a protagonist throughout most of the series until the last few episodes of the final season, and her switch to a villainous persona felt rushed.  Similarly, some viewers believed that arcs for other main characters, including Jaime, Cersei, and Tyrion Lannister, Brienne of Tarth, Jon Snow, and others, were adversely impacted by the quick pacing of the final season and did away with much of those characters’ development over the course of many years.  Others were confused and disappointed that Bran Stark became king of the Seven Kingdoms (and ultimate winner of the titular “game of thrones”), as there seemed to be little build-up or motivation for that narrative decision.  Many suspect that George R.R. Martin, author of the “Song of Ice and Fire” series of novels on which the show was based, may have anticipated providing more narrative context and development for these choices in his then-unpublished final novels in the series, and that the television series simply needed to end well before Martin could complete his novels.