Management requires smooth process, leadership requires clear vision
Management is about running systems, processes, and people.
Leadership is about taking action, and inspiring others to do so. Having a vision, and the ability to influence and motivate others to sail towards it.
Your team needs both.
If you have no managers, then key details, tasks and deadlines are likely to be missed.
No leader, and your team becomes a ship without a rudder. You are likely to become lost at sea.