I know this theory is unlikely. However I believe it is interesting to consider. (If someone else had this theory before me than I apologize).
I think there is a possibility that there is a small group of surviving Uchiha,(or perhaps just a single Uchiha, but I'll call it a group for now). When the Uchiha made an alliance with the Senju, they refused to join and hid themselves.
They didn't trust the Senju, but they also feared them, so they kept themselves hidden.
When Madara decided to betray the Senju, they decided to help him. After Madara lost to Hashirama, they saved his life.
Later on, something happened that made them realize that they could never reveal themselves. I'm talking of course about the Uchiha Massacre. More than ever, they realized that they must stay hidden.
I don't think they approved of Madara's Project Tsukiyome, which is why they didn't join him. However they dared not reveal themselves to fight him.
Currently, they want to stop Madara from destroying the world. However, they know that they cannot reveal themselves to anyone for fear of being massacred. Therefore they decided to save a fellow Uchiha who they believe could stop Madara.
I think there is a possibility that there is a small group of surviving Uchiha,(or perhaps just a single Uchiha, but I'll call it a group for now). When the Uchiha made an alliance with the Senju, they refused to join and hid themselves.
You must be registered for see images
They didn't trust the Senju, but they also feared them, so they kept themselves hidden.
When Madara decided to betray the Senju, they decided to help him. After Madara lost to Hashirama, they saved his life.
You must be registered for see images
Later on, something happened that made them realize that they could never reveal themselves. I'm talking of course about the Uchiha Massacre. More than ever, they realized that they must stay hidden.
I don't think they approved of Madara's Project Tsukiyome, which is why they didn't join him. However they dared not reveal themselves to fight him.
Currently, they want to stop Madara from destroying the world. However, they know that they cannot reveal themselves to anyone for fear of being massacred. Therefore they decided to save a fellow Uchiha who they believe could stop Madara.
You must be registered for see images