Richard Thomas was one of few cast members to be carried over from the 1971 TV-movie, The Homecoming: A Christmas Story, that begat The Waltons TV series.

And after more than 120 episodes, his name was synonymous with the central character/narrator of John-Boy. As such, it was jarring when Robert Wightman took over the role in Season 8 — though Thomas, who had left to pursue other interests, would later return for the occasional TV-movie reunion.

https://tvline.com/lists/recast-tv-roles-explained/true-blood-james/

They should have kept RT but never shown him.

Richard Thomas explained why he had to leave ''The Waltons'' (https://www.metv.com/stories/richard-thomas-explained-why-he-had-to-leave-the-waltons)

Thomas didn't intend to play John-Boy forever.

It surprises me that most women consider Thomas to be more handsome than Wightman, it seems. I would've thought the opposite for sure. Although that's a really bad photo of Wightman.