Hand writing gives your mind time to digest its thoughts
Something I’ve noticed for myself is that writing freehand, since it goes slower than the Speed of thought, allows my mind to wander and think about its own thoughts. This gives the mind a chance to find insights. I’ve observed in myself and in others that handwriting gives one the time to sit on a thought long enough to have a new perspective on it.
Perhaps the motor function of writing is part of this. I notice similar effects while walking and thinking too, though not always in the same way. It seems like the mind needs to be given a chance to meander, almost as if when the body is busy doing something else (writing, walking) it has a chance to actually not worry about what to do next and instead just relax on a thought and potentially discover something new about it. This feels in some way similar to Diffuse Thinking or Benefits of walking.