Nobody in the streets of King's Landing had done anything to her.

Something like this would've even made more sense:

Dany hears the bells, knows this is supposed to mean surrender, but doesn't trust anyone (Tyrion, Cersei, Jon, whoever) and is still seeing red about Missandei, so she flies right at the Red Keep and destroys it (killing hundreds of civilians in the process.) Tyrion/Jon/everyone is horrified at her disregard for the innocent people, she sees it as a cost of doing business when you want to rule Westeros. She still does an unquestionably bad thing, but it's more in line with both her character and the themes of the series. Both of those sides would be right and wrong simultaneously.

Instead she went out of the way to fry a bunch of randos before eventually going to Cersei, because that's something a Mad Queen would do.