Must be real money prediction markets. Based on credible reporting, does not need to be a conviction. Conspiring with others to start a fire, bribing someone to start the fire for you etc. is enough to resolve YES, if it results in an intentional fire. Actively helping an existing fire to spread, including making it difficult for firefighters or other services to respond to the fire appropraitely (or conspiring to do it) is also enough to resolve YES. Inaction is by itself not enough to resolve YES.

Partly subjective resolution, won't bet on this market.

Context: People are making wildfire bets on prediction markets. Experts say it could lead to disaster | CNN

People are making wildfire bets on prediction markets. Experts say it could lead to disaster | CNN

As the catastrophic Los Angeles wildfires raged last year, people placed bets on how how many acres the fires would consume, which locations they would reach and when they would be contained.