Agency

I am wondering whether agency, as the ability to change a state of affairs, is a good thing. Yesterday while looking for a novel, I found my mathematics final project. I amazed on how the book was mostly consist of formulas, with acknowledgement longer than the introduction and conclusion (since basically I only need to say QED). I even managed to write a book about numbers, have one citation for the math book and write a popular writing about mathematics in a local newspaper. So why did I change my discipline? Why path dependency did not work for me?