I wouldn't say Dany has been crazy, but it's been clear for a while that she wouldn't exactly be a merciful leader. Her answer to pretty much every challenge is Dracarys.
Again, I'll repeat it. Ever since she got to Westeros, she's been wanting to burn down King's Landing. Tyrion had to beg her not to do it. This chick was basically operating under the idea that when she got to Westeros everybody would flock to her, and when didn't she just wanting to start burning people. She was always a questionable leader.