Why did Trigun become Trigun Maximum?

Yasuhiro Nightow first published a Trigun one-shot in Tokuma Shoten's Monthly Shonen Captain on January 26, 1995, and regular serialization began in the same magazine two months later, on March 25. The magazine then ceased publication on December 26, 1996, and the series was put on hiatus, unfinished. Tokuma Shoten collected what existed in three tankobon volumes, released from April 25, 1996 to January 20, 1999.

Shonen Gahosha's Young King OURs approached Nightow next, and the documented detail matters: the magazine was interested in him beginning a new work. Nightow, however, was troubled by the idea of leaving Trigun incomplete, and requested to be allowed to finish the series. The manga resumed in the October 1997 issue of Young King OURs under the title Trigun Maximum, and ran there until March 2007. Shonen Gahosha collected Maximum in fourteen tankobon volumes, from May 23, 1998 to February 27, 2008, and republished the original Trigun chapters in two volumes on June 2, 2000.

Nightow has stated the verdict himself: there was no difference in the story between the two titles, and the only reason for the change was the switch of publishing house. Maximum is a continuation of the same series under a new roof. The story itself picks up two years after the events that closed the original run, which is why the second title can feel like a sequel on the shelf while being, on the record, a resumption.