Why place a turret amidships?

What advantage did a center turret offer compared with putting three turrets forward and two aft?

The tradeoff centered on weight distribution and metacentric height.

Concentrating three heavy turrets forward changes how weight is carried and can complicate a ship's stability characteristics. Metacentric height and weight distribution are the reasons a designer might accept an amidships turret despite its restricted firing arcs and awkward machinery arrangement.