He does seem to be a victim of circumstance. But, isn't he in Last Crusade as well? He declined Donovan's offer to head the Grail search, and actually went looking for his dad, a circumstance he couldn't ignore.
I think that's one of the appealing aspects of Indy. One reason I've argued before about his being more mercenary than hero. It's believable. We, that is, the general public, are more self-serving than we like to admit. A traditional movie "hero" is just too distant from us. They're fun to watch, but they're not US. Indy, on the other had, could easily be us, or rather, we could easily be in his situation and act as he does -- self-serving. That puts us more into the movie rather than watching it from a safe distance. I believe if Indy was the big, goody-two-shoes hero, we wouldn't like him nearly as much.
Temple of Doom just shows this more clearly than the other films ('cept maybe Raiders, where he is being paid to go after the Ark). And maybe that's one reason people don't like this film as much -- It's a dark mirror where their subconscious sees a rather unwelcome reflection. It's easy for us to delude ourselves and imagine we're all good, with no skeletons in our closet, and it's certainly what most people tell to others. However, when watching Temple of Doom, it's difficult for us to imagine and emotionally agree with ourselves that we'd do anything other than leave the village, or try to save our butts first and foremost. In other words, when watching Temple, we're drawing more into survival mode and it's harder to imagine ourselves being heroic.
That, to me, is one of the genius subtleties of Temple Of Doom. We're tricked into feeling this darkness within ourselves until the third act, which to me starts when Indy recovers from the potion. We feel heroism, long kept caged, being allowed to rise, and it explodes when Indy beats the crap out of the first guard (that Williams' cue is pure magic -- we FEEL being heroic at last).