The 9 tails power itself represents the physical power of the sage of 6 paths. The sage of 6 paths separated the tailed beasts from the 10 tails. All of the tailed beast especially the 9 tails basically have the power of the of the sage of six. When naruto started to give away his power to the other ninja this made madara pay closer attention. I understand why madara out of all of the tailed beast took control of the 9 tails. Madara, during the fight with the first hokage made the 9 tails modify his chakra. Therefor turning the 9 tails chakra into his. The 9 tails thinks like a genius ninja. Maybe has the smartest ninja mind we seen in the manga. He learned all his techniques from the sage of 6 paths. That's why out of all the beasts the hidden leaf village kepted the 9 tails and let the other village had the other beasts. So guys what do you think?