I think the idea behind the formation, or at least it's renaissance, has come from Thomas Tuchel. Nagelsmann worked under him for a time at Mainz.
Tuchel calls it the 'box formation' - because of how the 4 centre midfielders are set out - he has said he thinks it's where football is headed in the near future.
From what I know of Nagelsmann, he doesn't put much stock in formations at all, he believes you adapt to the players you have, that a coach's 'social untelligence' is the vital quality that determines success. How well a coach can understand the personalities in his squad, and then communicate effectively with them and get them to pull together.
