For months, speculation around the prosecution of Donald J. Trump has focused on one key question: How would special counsel Jack Smith establish that Trump’s words and actions led to the violent upheaval of Jan. 6, 2021, when a maddened mob of his supporters crashed through barriers, beat Capitol police officers, broke into House Speaker Nancy Pelosi’s office and threatened the life of Vice President Mike Pence? A grand jury’s conclusion, unveiled in a four-count indictment released late Tuesday, was devastating in its simplicity. While the Jan. 6 riots were clearly criminal, they are not the...