The programming in earliest electronic computing machines was synonymous with connecting wires to plugs. Layered architecture doesn't exist. So, programming a computer was a feat of electrical engineering same as it was an exercise in algorithm design.  

John W. Mauchly and J. Presper Eckert proposed an easier way to change the behavior of their calculating machine. They considered that the form of mercury delay lines as memory devices to provide a way to store program instructions. This helps to avoid rewiring the system each time it had a new problem to solve, or an old one to debug. 

The main difference von Neumann architecture and its predecessors is the way how they store the program. In its predecessors, there is no way to store the program. But in von Neumann architecture, the program can be stored. 

All stored-program computers have come to be known as von Neumann systems using the von Neumann architecture.