Complex sentence: For the first time a whole issue was devoted to a single tribe, attributed to Gertrude Simmons Bonnin's Sioux patriotism and her effort to enlist the renewed interest of Charles Eastman in the Society.
Split into simpler sentences: For the first time a whole issue was devoted to a single tribe. In all likelihood, it was evidence of Gertrude Simmons Bonnin's Sioux patriotism and an effort to enlist the renewed interest of Charles Eastman in the Society.