All businesses must have a plan. That is absolutely applicable to the Dallas Cowboys, because the NFL is a big business. But there is a funny thing about plans. They tend to only work when the assumptions used to make them are correct. And they almost never are.
All teams deal with this problem. Some are very poor at it, while others seem to find ways to roll with the changes and adjust things. It is understandable to feel that Dallas falls into the first group. This offseason has seen several unexpected issues crop up, and the team seems to be scrambling.