Why did the Mark II turret become heavier?

How did the Mark II turret end up heavier than its predecessors?

Design additions made the supposedly reduced mounting heavier, though this brief answer does not identify the specific changes.

The answer is deliberately brief: additions introduced during redesign made the later mounting heavier. It identifies redesign as the immediate cause of the weight increase without giving a component-by-component engineering explanation. The reply also does not quantify the added weight. A revised mounting can accumulate weight instead of automatically saving it.