Old Tom Morris said:
I don't think anyone with half a brain doubts that something like this was in Dany and the potential was brewing. It's all about the final step being such a big one and how quickly/harshly it contrasts to what she was just willing to do in the North.
I think something as simple as losing Rhaegal in battle vs in a dumbass way to Euron that everyone hated anyway would have helped immensely.
vs. what she did in the North many many things have changed since then
1. she doesn't have the best claim to the throne and while she knew that before the BOW she had no time to process it and we didn't know if she even believe it. She basically found out just as the horns sounded the battle was on. And her most trusted bodyguard died in the battle someone she KNOWS loves her.
2. she was not hailed nor loved by anyone in the north - they fought her very step of the way
3. she was then betrayed by Jon/Aegon she feels when he told Sansa and Arya
4. she lost another dragon (whatever you think of how it was done)
5. she had one of her most loved and trusted advisors killed before her eyes by the enemy
6. she felt betrayed by Tyrion when he did not come to her about Jon/Aegon and went to Varys instead (behind her back)
7. she was betrayed and perhaps even poisoned by Varys
8. she felt betrayed by Tyrion again about Jamie - just meaning he was captured returning to KL and Cersei (talk about a quick reversal of direction)
9. and finally it is likely she knew about Tyrion letting Jamie escape before the battle as well
3 huge deaths - Missandei, Jorah, Rhaegal
3 betrayals - Jon/Aegon, Tyrion more than once, Varys
No love from anyone
Lost her inside rail position for the throne on the homestretch
It really is not a question of whether it was always possible - on that we agree.
The only question is if the turn was justified. That's sort of more of a philosophical question. If the seeds were always there, were those deaths and betrayals and the sense of despair enough??
To me - yes unequivocally.
And we may find out more after the fact here - they may reveal things in the finale that Dany knew or felt that we were unaware of. And they did not show them up front because it would give it away.
But I think the issue here is not whether she was capable, nor whether it was morally justified. I think the entire issue is one of self projection. I just think 99.9999% of people putting themselves in the same position even given all that happened would NOT do that. But she did. To rational people, irrational steps are never justified. But you can't just assume she is rational at that moment just based on what she has done in the past. She snapped. And people don't like that (particularly for a character many liked or loved and hoped would be different).From a storytelling point of view too - as watchers - narratively we want more morally justifiable reasons. But that isn't always the case (in real life). People snap and we don't know why - hundreds and hundreds of things happen along the way none of which made them snap.
It's like saying any serial killer always had it in them and showed all the signs in retrospect - but right up until they did it the first time they were not a homicidal maniac. Something or some things trigger that first time.
It's like every news story about some nut job mass murderer or spree killer - the signs were always there and yet nobody saw it coming or did anything to stop it. Because we rely on the fact that 99.9999% of people don't snap.