They have been hinting at it the last two seasons, I agree it could have been done better. But:
"You have to find a way to make her listen." Varys speaking to Tyrion after Dany burns the Tarly's.
Her and Sansa's little talk before the Long Night was clear foreshadowing that Dany would not give up the North and would probably kill Sansa if she doesn't bend the knee. I'm sure Jon would be really happy his girlfriend burned his little sister alive. Brothers are usually cool with stuff like that/s
"You laid down your crown for the good of the people would she do the same?" - Sam telling Jon that he's Aegon.
These are just off the top of my head.