Take the area of women's political empowerment as an example. We have the National Commission on Status of Women, the League of Women Voters, Women in Democracy, Institute for Education in Democracy etc basically doing the same thing. This simply means that if your work is similar and you share similar goals, then you must work together. Donors get confused when you come with the same set of proposals and aims. For your own survival as an NGO, it is necessary to team up.
Networks also help invaluably when protection from the authorities is considered.
You have greater impact working as a team. It is wrong, nonetheless, to imagine the activities of NGOs as a whole are pure and straight. Not all of them are transparent. Few have regular and independent audits. Fewer still publish their accounts.