Yeah, everyone reacts to all fantasy series the same as this... oh wait, nope. I mean, LOTR ending is actually a bit, meh, overly long and a bit woo, everyone is great, but it's still great. Most books I read, or tv I've watched has done okay. Sometimes they go a way I wouldn't prefer, there are always characters people hate to see succeed, fail, die or whatever. But people loved Robb, and he got absolutely destroyed, and everyone around him, and people were surprised but it fit.
There is a huge difference between things turning out unexpectedly and just being utterly utterly stupid and literally the show writers have said straight to our faces, the fans expected certain things so we changed them for that reason alone, not for good writing but if people predicted things that's bad (even if correct and make perfect sense, planned for 5 books) so we changed it completely.
There are loads of books/series in which the guy I wanted to 'win' died, or the bad guy gets away with it, or manages to live, but there are very few books and literally no good books I've read where in the last two chapters everything from the rest of the book was thrown out just to be unpredictable.
Lets assume that GRRM meant to put Jon on the throne, then there are million ways to get there, just because fans figured that out, because it felt right, doesn't mean it's predictable. But then they rewrote the series essentially to have someone else 'win', and in fact in doing so they broke it completely. Bran now controls a throne, with no army, in which one of the kingdoms broke away with zero consequences, so the rest of the kingdoms can look after their own, after years of war and heavy taxation, heavy losses in supplying the iron throne with support or Robb, or Jon, etc, or give Kings Landing shedloads of cash to rebuild which will take decades and is a disaster zone. In other words the guy who won the game of thrones, was also written into a position where every kingdom will break away in days, and maybe Dorne or someone else will say, everyone is ripe for conquering right now, it's just plainly stupid. Sansa breaking away to become a queen, having never led, having never led any men into battle, having never made a good decision in her life and destroying the 7 kingdoms with her decision to split away... is suddenly a beloved queen?
It's just a joke.