The alchemist burning out could be due to overexertion of their powers, a confrontation with a powerful enemy, or even a internal conflict within themselves. It adds drama and complexity to the comic.
It could be due to overwork or creative exhaustion. Maybe the alchemist characters face too many challenges without proper breaks.
Maybe he has some kind of psychological issue or was under a bad influence that led him to do such a thing.
It could be due to engine failure or overheating. Maybe the cars were pushed too hard and their components couldn't handle the stress.
Maybe the kid was having a bad day and took it out on the comic in a moment of anger.
Maybe the alchemist broke some important rules of the party or had a conflict with the leader.
The alchemist might have been kicked out because of a betrayal, or maybe his methods and ideas were too radical for the rest of the party to accept.
The reason could be that the cartoon creators wanted to show something visually impactful. Maybe the cars are in a race or a chase scene, and the smoke adds to the intensity. Also, it could indicate that the cars need maintenance or have some kind of mechanical failure.
It's hard to say for sure. Could be that they were trying to be rebellious or just doing something without thinking about the consequences.
In the comic, Daenarys indeed burns Jon Snow with dragons. This event has a major impact on the story and character developments.
Maybe because they have some kind of conflict or a mission that requires their interaction.