I think this guy hits it out of the park with his review:
It isn’t that Dany slid into madness. It’s that they did not build into it with the writing and it came off as rushed. Just three episodes ago she was riding her dragon with Jon and wishing they could just disappear.
Yes. A slow approach would have been better.
The loss of Jorah could be shown to devastate her.
The loss of Rhaegel could be shown to have her teetering on the edge.
The loss of Missandei could be shown to have her slide into a whole new personality.
The betrayal of Varys could be shown to have her despise everyone in Westeros.
The writers sort of “went there” but it looks rushed and fails to show a sufficient descent into madness. It just really comes across as a plot twist: “And in this episode, Dany goes crazy!!”
She’s always been a psycho.
She crucified the great masters of that town back in one of the first seasons.
This episode hardly surprised me.