Going to again borrow an external article, because it eloquently expresses my feelings about this episode:
Game of Thrones Season 8, Episode 5, "The Bells", needed to earn Daenerys' fateful decision, but Matt Goldberg explains why it failed to do so.
collider.com
"The failure to justify Daenerys’ choice to raze King’s Landing is emblematic of the show’s rushed conclusion and how it has failed her character and her story. Given more time, we could see Daenerys’ descent from confident ruler of Essos to isolated, paranoid maniac. Given more time, we could see how greatness morphs into madness and no notices or comments because they’re attached to an ideal or they’re willing to ignore clear warning signs (like executing innocents as opposed to people who have tried to kill you or enslave you). There is a way to get to Daenerys, flying high above King’s Landing, deciding to burn the whole thing down even though she’s already victorious. But “The Bells” didn’t get there. It wasn’t even close."
EDIT - actually the following was the article I actually went to that site to read, as the writer makes me laugh with his GoT recaps each week:
Game of Thrones' penultimate episode, "The Bells", saw the arrival of the Mad Queen Daenerys Targaryen - we dive into the biggest theories and questions.
collider.com
And not only did he make me laugh again this week enough to want to share it on here, he also again expressed sentiments that echo my feelings about the direction the show took last night.....in slightly more colourful language.....
But much like a significant portion of Thrones‘ back half, the writers just didn’t put in the work. Almost, but not quite. There’s a thin but definite line between ruthless (Tywin Lannister) and batshit murderous insane (King Aerys II Targaryen), and Dany has always straddled it toward the ruthless side. Torching the Unsullied’s masters in Astapor. Crucifying the slave masters in Meereen. Executing the Tarlys. Being super okay with boning her nephew. Most of these are, obviously, not very nice things, but they’re not cruelties, they’re means to a very clear end: Dany winning the throne. That’s what sits awkwardly in her destroying King’s Landing…she had won. And the moment she kept going past that victory she leaped from ruthless to cruel with nary a hint of warning. Being rash and petty and flying straight to the Red Keep to BBQ Cersei for the lols? I’d buy it! Burning innocent children in the streets? An unexpected development to say the least!
You just gotta work with the evidence you yourself provided, you know? It’s like if Benioff and Weiss decided to have Tyrion f**k a pie, right, like mid-episode just cut to Tyrion absolutely going to town on a freshly-baked pie. A few of us would probably be like “that seems a little out of character.” Imagine if the explanation from the showrunners was then, “Well, we’ve shown Tyrion having sex before.” That’s not the same! Adjacent, certainly but not the same. If you want to have a character end up as the pie-banging guy, you need to dutifully plant that seed for longer than an episode and a half. If not, you’re just, you know, you’re just having a guy f**k a pie. 
