A lot of folks here blaming D&D 100%, but they shouldn't be taking all the blame.The thing is, the writer himself (George RR Martin) has specifically stated this was how the books were supposed to end.
This was the deliberate plan, Daenerys was supposed to go crazy from the jump.
But really think about it - this plot all its characters, etc. were written and thought of nearly 30 years ago, when the books started.
Martin probably never saw the minority and feminist movement of social media coming. This book and television series is an example of old-fashioned thinking, because it was created by old-fashioned thinking and perspectives. The minorities and their pretty beauty queen were supposed to lose.
Those "pretty" white women and minorities weren't really a part of the dungeons and dragons scene back then, so this story really wasn't supposed to be for them (us).
Which goes to show: this is what happens when you're not thinking globally - your product, reputation and legacy suffers. People are not going to be nearly as interested in the prequels, merchandise sales will drop, etc.
I honestly think this is why D&D were kind of like "breh, we're going to turn off our cell phones and take a vacation." when they were asked what they were going to do during the last episode. I seriously think they knew the ending was going to trigger a lot of folks. I wouldn't be surprised if they tried to sway Martin somewhere later down the line but dude kept to his guns.