Most negative opinions I heard and read were not about the fact that Dany turned evil - this has been telegraphed for a long time and most have expected it. It's that the transition was almost completely unmotivated. It makes no sense whatsoever. People want to understand the characters, that's the central point of this article.
The underlying character needs and triggers were established over many seasons, and the multiple triggers were laid on heavily throughout S8 (and some pretty heavily in S7.)
The idea that the actions were unmotivated is bizarre; I get that some fans were hoping (and that narrative convention supports those hopes) that Dany would transcend her clearly established flaws, but the idea that there was anything not clearly established, in either general orientation or specific triggers, is hard to believe.
