I was thinking about this movie recently. The prevailing wisdom in screenwriting is to make the hero character fundamentally yourself. If you analyse the Will Hunting character in that light, it tells you something about Matt Damon. He went to Harvard (English) IRL. Apparently he fantasizes about being a misunderstood genius and being able to use that to credibly peddle his political message.
I also feel compelled to say as someone that was an actual math “genius” (which in truth means little) in school IRL that I always feel insulted by stories about such people. After thinking about it I now easily see why this movie was a hit and why Matt Damon became popular. It strokes the ego of anyone that shares his trite observations and sentiments about the world and inane behaviour. Here is a 2 minute video that is far more entertaining than that whole movie and helps to realize how bad it is and what kind of person likes it (hint: not math geeks). The character is comically absurd and that absurdity packed into endless subliminal messages is what the script is ultimately about.