In TLJ documentary, Johnson paints a picture of a more active role to Luke’s exile, him realising that the cycle of jedi and Sith ascendancy was never ending and so had to be broken, by removing himself and the jedi, out of the picture. The force would then have to choose a worthy inheritor of the light.
Pity the idea was executed half heartedly in the film.
That’s almost verbatim his dialogue in the film. It’s established really well.