Leonard Cohen reached adulthood and chose to write poetry and novels at a time when it was unusual for singers to write their own songs. Not so long later, in 1962, the singer-songwriter was co-introduced by the Beatles and Bob Dylan. Now I know there were singer-songwriters before then, but less prominent.
But if Leonard Cohen had begun his musical career, say, in his early twenties, he would have had a head start on introducing the singer-songwriter and in putting poetry into music.