[Phylum]

^ Don't listen to this clown, he's sympathetic to the Blackfyres.

Still the Mad King thing was set up in the show, even with less detail. Like I'm pretty sure they mention Duskendale in the show and him never being the same after that. And I'm certain they talk a little bit about his beef with Tywin, and Joanna. Plus Targaryan madness is a well documented thing - Aerys was one of many to marry his sister. They're all inbred lunatics, except maybe Rhaegar who seemed to have the right ideas and was seemingly ready to overthrow his father before he died.

Also a fun thing I noticed the other day - if you discount Aerys and his descendants, Robert Baratheon was probably next in line for the crown. Robert's grandma was Aerys' aunt. For all he hated the Targaryans, Robert was the first son of the first son of one.