Watched this last night. Thought it was great.
I thought the moment Dany decided to light everything up made sense considering the development of the character. Homegirl has achieved absolutely nothing in the series via diplomacy, as she has never really bothered to truly learn it. By its very nature, you'll take a few Ls, but end up getting what you want over time. Any time she's faced any kind of pushback, she's basically just lit them up and rolled out. She's always reacted in situations that needed a lighter touch with sadistic violence.
On top of that, all of her ruling has been over subjects who were happy that she wasn't enslaving them. They were all willing to get on board because they knew it was going to be an improvement. Now, she doesn't have the crutch of offering freedom, and is shocked to see that people like other options better than her, and doesn't know how to respond, especially with the alienation she feels with all of her advisors betraying her. She accepts that respect won't be how she rules, and says that she'll need to make people fear her.
When she looks at the Red Keep and says fukk it, that's pure entitled rage. In her mind, there shouldn't even be a war, and that shyt belongs to her. So she came after it of the mind that she'll destroy her own belongings if she feels like it, and wanted to make sure she had a hand in killing Cersei. But most of all, like someone else mentioned, killing innocent people puts fear in all the common folk that she is not to be questioned.
I'm excited for next week, assuming they follow up on who, exactly Varys was sending letters to. I'm also assuming that the letters were to inform others of John's lineage, and possibly absolve him of any wrongdoing in the attack on King's Landing.
Exactly