I think he understands. He just doesn't care. He's singularly focused on Jenny right through a bunch of dramatic historical events we value as the audience.
In the film he scored a 75 on his IQ test. That's in the range of "borderline," not mental retardation. To me, his story was about embracing destiny, overcoming ones own limitations and maintaining a positive attitude in life. He was also great at loving people unconditionally.
I suggest reading the book. In the book he is an idiot savant and is doing advanced mathematics. They “simplified” a lot about his character in the movie.
I've always thought that Forest Gump was about accepting what life throws at you. He doesn't fret or question the things that happen to him, he accepts it and does his best to adapt and make the best of it. I found this very comforting at the time for reasons I can't entirely explain.
NGNSteveTheSamurai t1_itiw4ku wrote
Nah man the whole conceit of the movie is what if a slow person didn’t realize they were a part of a bunch of historical events?