First, if you have the ability to spearhead a new campaign, the chances are that your skills are better used further developing the strategy, and perhaps coming up with other new ideas. By doing the work yourself, you're failing to make best use of your time.
Second, by meaningfully involving other people in the project, you develop those people's skills and abilities. This means that next time a similar project comes along, you can delegate the task with a high degree of confidence that it will be done well, with much less involvement from you.