Breakthroughs rarely, if ever, occur in just one place and by just one person. People build upon work done by others. Consider Newton and Leibniz and their simultaneous development of calculus. Or how Einstein built upon Maxwell.
In the case of a medical researcher there would be reams of data, lab books, discussion with others in the field who are pursuing a similar goal. Not as much fun as a juicy conspiracy tale.
Most of your post is correct. But while Leibniz had a superior notation to Newton’s, it’s quite historically clear that he did not simultaneously develop anything. Europeans advanced that myth, because they resented an Anglo physicist getting the credit. Newton showed Leibniz some of his work, he did not independently develop calculus. He stole it and took credit because Newton did not publish the work until years later.