Lewin emphasizes that the desires and motivations within the person and the situation in its entirety, the sum of all these competing forces, combine to form something larger: the life space.
Organisations, groups or departments start small with individuals/leaders laying the foundation to create a new system. As more individuals join the system, the interactions creates the emergent properties.
If the environment is purely based on command and control, the individuals joining the system either have to accept the laid out rules or gets rejected by the system. However, as the environments becomes large and complex, the structures governing the system needs to be redefined keeping the goals in mind.
Leaders play a critical role in laying out the appropriate structure to drive the systems behaviour to achieve the needed goals. These structures in turn leads to creation of the culture. Unfortunately, large organisations struggle quite a bit as we don't have enough leaders with the knowledge of Systems thinking.