Don't do a web search for "first man to split the atom," you'll get several different answers.
But there's general agreement on the first scientist to create a controlled nuclear chain reaction: Enrico Fermi, who fled Mussolini's Italy for a new home in the United States. Fermi's talents went beyond soaking up knowledge; he could also explain science to the world at large.
He is celebrated in David N. Schwartz's book The Last Man Who Knew Everything: The Life and Times of Enrico Fermi, Father of the Nuclear Age.
This interview from 2017 covers some of the highlights of an illustrious life.