The correct answer to this open question is the following.
The relationship between reading long-form texts and the development of certain skills is that reading long-form texts requires a special concentration to focus on the story, characters, events, situations, contexts, while you are processing that information in your brain.
When reading this type of text, you developed skills such as focus, understanding, taking notes, improve the capacity of your memory, and the mental agility. Of course, it also helps to increase your culture and knowledge that can be used in other situations.