One of the very best managers ever were attackers or strikers - Lattek, Fergie, Cruyff, Zagallo, Busby, Clough, Hitzfeld, Lobanovskiy, Michels.
Others were defenders like Beckenbauer, Trapattoni, Herrera, Paisley, Happel, Lippi, etc.
Of course there is a plethora of midfielders like Capello, Ancelotti, Miguel Munoz, now Guardiola.
Not sure if there is a correlation in it to be honest, but those who were really visionaries in the past were either attackers or defenders. Midfielders generally got great results and were successful but didn't really create an ideology or something revolutionary in management.