I don't think Dany's mental demise was foreshadowed at all in the books or the TV series (except maybe when she crucified the slave masters in Meereen). She has probably gone through more adversity in her life than any character in the series but always strived to be loved by the people and wanted to be the great "breaker of chains." Suddenly, over the past couple of episodes she falls into madness that quickly? I think it's just another example of sloppy writing by the folks at HBO. It is entirely possible that when GRRM gave D&D his outline of how the story ended, he may have said Dany eventually goes mad and he's going to play that out in more detail in the 2,000+ pages he's still planning to publish but HBO has just been trying to cram that into a few episodes.I know it's been "obvious" for a while (back to Season 1 according to some people, like my fiance) but I was still angry and disappointed in Dany for her fiery decision. Guess it's good old Jon boy for King.
And a little disappointed in Jamie, but not surprised.
Cleganebowl 2019 was epic, though.
Vary's death was another really stupid one. The man who has easily been one of the most cunning in the series and only wants good for the realm suddenly decides to start talking openly about supporting a coup with Jon Snow.