After 24 hours to contemplate, & after a partial re-watch last night, here's my take on the destruction of King's landing: It was the calculated put the fear of God moment into Cersei by Danaerys.
Fact: The Mad King had deposited stores of Wildfire beneath every important building.
Fact: Cersei had asked HER Hand if the rumors were true before ultimately blowing up the Cathedral of the Seven Gods with wildfire. If the stores were widely rumored, then Dany had to know about them due to her lineage, & the fact that Cersei had demonstrated their existence.
By taking the thermonuclear approach to Kings Landing she accomplished the following:
1. She destroyed those munitions so that they couldn't be used against her in the future
2. She checkmated Cersei:
Cersei wasn't afraid to use wildfire, as she had blown away her enemies with it in the past. She didn't care about the citizenry, she only used them as a shield. Her fatal error was not taking Dany's determination into account. She thought that Dany would spare the common folk if her armies surrendered, OR she would blow up Dany's forces & sack the City herself with wildfire to win the battle. She also erroneously thought that her batteries of Scorpions would take out Drogon.
Danaerys's statement in effect: You've opposed me on every occasion: You refused to join the fray against the White Walkers, & instead fortified yourself with the mercenaries of the Iron Bank. You
refused my surrender terms & invited this battle by slaughtering Missandei in front of me, thus inviting my death sentence upon you. I've destroyed your troops, your weapons, now I'm going to destroy you!
Danaerys has been consistent: You bend the knee to her or you die. If you break your oath to her, you die.
The only problem is that she has backed herself into a corner with this approach. Kings Landing can be rebuilt. The public trust is another matter.
