Jack Johnson was heavyweight boxing champ of the world in 1912; he was African-American. He was refused first class passage on RMS Titanic. When the ship sank, the folk world reacted as if it were a judgment on segregation by race, class, etc.

Mance Lipscomb does another song, entirely different but on the same subject, playing slide guitar on it.

Jacob Astor was a millionaire; he had plenty money to spare,
But when the Titanic was a-sinkin', Lawd! he could not pay the fare
, God knows; all the people had to run and pray.

CC