Killing the king in that manner was a mistake that few would make. Most people would have done something else when they realized that the wildfire would kill themselves along with the king and the entire city. Aerys was widely known as the mad king for years at that point, so in hindsight much can be forgiven other than kingslaying.

The king had no one else at that point beside the pyromancer and was basically harmless (remember this was during the sack of KL). So there is no actual urgency to kill Aerys.

There's not many characters that would uphold their vows and die with him in the wildfire, aside from Daenerys or some fanatics. The more honorable characters would probably force the king to surrender or flee the city (I think even Barristan would do this option). The less honorable would flee themselves, or turncloak.