I don't believe people burn things down just for the fun of it, generally anyway. For this reason I believe the act of arson can usually be attributed to some form of revenge. It is usually viewed as some form of aggression and there is typically are reason this aggression leads to an act of arson.
Yes, I think that arson offenders commit acts mostly out of revenge, because a person has to be very upset in order to do something so drastic. Other than insurance fraud, revenge is probably the main cause of arson. If someone is that upset, they are willing to set something on fire to get the person back.
Pyromania is one of several Impulse Control Disorders. Pyromania is characterized by an impulse to set fires, and involves deliberate and purposeful fire setting with tension or heightened arousal prior to the act and gratification or relief following the act of setting the fire. The fire is not set for monetary gain out of any sense of revenge or anger.
Some people set fires to remove evidence of other crimes (murder, burgulary, etc), others do it for insurance money. But it seems most fires are either accidental due to faulty wiring, unsupervised candles, embers from campfires, or something hot being too close to cellulose objects. And then lightening has been known to set fires.
I do not think that most arson is revenge. I think that it is mostly either because the arsonist is obsessed with fire and/or unable to control the fire they create. I don't think that most people who start things on fire are thinking "Yes. This is a good way to get revenge." I think they are probably not mentally normal thinking at the time they do the act.
Where I think it would make more sense if most arson acts were done out of revenge, I don't believe that is that more common practice. People love to do stupid things, and destroying things or burning things fall into that category. I would say a good number of arson occurs so people can benefit from the insurance fraud.
I think people who commit arson could be doing it for a variety of reasons, perhaps for insurance money or perhaps out of anger for whatever reason, I wouldn't say that you could call the majority of arson acts that are done out of revenge because there are so many different reasons.