Chamberlain was remarkable
And proof liberal arts professors are not as useless as you think. Rhetoric sounds like a degree I hear people complain about.
Our understanding of Gettysburg is due to him. When the park was formed and the "official" history written, his voice was first among equals. Oates, whom he battled on Little Round Top, was very bitter about Chamberlain's influence. But that was common after the war, what is taught as a key part of Shiloh never happened. But it made some Iowa units look good and their commander was in charge of writing the history.
Chamberlain took to soldiering. Part of it was his commitment, he was an abolitionist who felt his death was a fair price for the cause, at the same point he cared for his men and had a quick mind. And he had some luck.