Luke intimately knew the Scriptures, especially Isaiah. This is clear when we note how many times Luke quotes or alludes to the OT Prophet in Luke/Acts. James A. Sanders comments:
Luke’s knowledge of [S]cripture was rather remarkable. . . What is remarkable about Luke's knowledge of his [S]cripture was that apparently it came from his assiduous reading of it, or portions of it. ("Isaiah in Luke," 44)
Isaiah was so present in Luke's writing because Luke had let the Prophet's words permeate his mind and transform his life. In other words he binge-read Isaiah. Again and again.
May this same statement be applicable to modern day narrators of the gospel. Those that desire to faithfully share the good news, like Luke, should similarly be steeped in the Scriptures, OT and NT.