A business idea without proper management plan is one that can be considered to be dead on arrival. Business success revolves around excellent management plan first before capital size. With a large capital chunk into any business that's lacking in proper planning, such business can inevitably collapse, turning into a wasted investment.
Of course, the management plan will have a big role to determine the success of the business. Having inappropriate plan surely raises the chance of the fail because we may have no idea and be panic when we get the difficulties or too many challenges in the early stage. Also, an alternative plan is also important to deal with an unexpected condition while we are running the business. Moreover it is in the early stage, there must be always many things beyond our expectation.