Maybe because he himself is the fire? x)
Regarding the roles.
As for the Mafia, it's complicated. I can say with some certainty that it's not Arandor because of his voice on the first day. Vespers doesn't seem like a Mafia member, but I'm not sure about that. And it's definitely not me :D The others could be
Sezam might be a Cop simply because of the block, although he seems to be acting carefully. Gur is also acting carefully. Also, Arandor voted for Dag at the moment when it was essentially decided whether the idea would be supported en masse. It's generally beneficial for the Maniacs to have executions... although it's already getting a bit crazy, so I won't continue).