https://screenrant.com/ncis-agent-gibbs-exit-mark-harmon-comments/

Mark Harmon opens up about his departure from NCIS after playing the role of central character Leroy Jethrow Gibbs on the show for 19 years.

Why Did Mark Harmon Leave NCIS? (https://www.cbr.com/mark-harmon-ncis-exit-explained/)

Despite being NCIS's biggest star, Mark Harmon left and stopped portraying Leroy Jethro Gibbs in the show's 19th season.