Does the success of a group depend entirely on the ability of its leader?

I'd say leadership is crucial but not everything. The main reason is that even the best leader can't succeed without a team that collaborates well. For example, in my UI design work in Shanghai, we had a project where our manager was excellent at planning, but some team members didn't communicate properly - it caused delays despite the strong leadership. That said, a good leader can bring out the best in people and coordinate efforts effectively, so their role is still central to success. It's more like the leader sets the direction, but the whole group needs to move together.