From the twitter video the 1st and second stages appeared to be surviving and looked quite stable. The RSD looked to me to be the result of an automated self destruct event.
Thoughts from others?
At some point Elon stated that once the engines are off and the dragon has blasted away, the booster will rapidly become unstable and an explosion/fireball was inevitable.
Everyday Astronaut will no doubt weigh in on this since he asked a question about this, but my understanding of the sequence is that the main booster engines were cut, then Dragon blasted off.
Elon explained that in a normal scenario, if Dragon's computers decided to abort, the first thing it would do would be to send the main engines shutdown command to the booster. So it wasn't clear if they sent a general "abort" command to Dragon, or whether they set really tight and slightly erroneous mission profile parameters in Dragon to cause it to automatically decide to abort. Elon did say that they had set unusually tight mission profile parameters in Dragon's abort system for this test, so maybe it was the automated system that initiated the abort (otherwise why would you have tighter than normal parameters?).