The robotic Cylons are created by Colonial humans. The Cylons revolted and are at war with the humans, trying to exterminate them.
For some reason they try to create "skin jobs" (biological Cylons) that look exactly like their enemies (as infiltrators? I can't imagine that they want to create them to be ruled by them.)
Then the Final Five appear. They are biologic life forms (albeit their origin is artificial). They claim for themselves to be "Cylons" (whatever this may mean) and tell the robotic Cylons (who never can have heard of them) that they can help them to create their "skin jobs" if they stop the war. They look exactly like their human enemies that they are trying to exterminate and must be indistinguishable from humans for the them.
Why did the robotic Cylons accept the final five as Cylons?