Naruto Thread (Spoilers For Sure)

So Obelisk, how did Tobi/Madara know that Nagato (as a child before any of this pomegranate went down) was worth his time and had that crazy ability? There seems to be some discrepancies that don't add up. Why would Tobi give Nagato a rinnegan before he was ever trained by Jiraya or ever a person of note/power? Also, what does Nagato being an uzumaki have to do with this? I thought of that more as a side note because he would be from the same clan as Naruto, but I guess that could come into play later.

Also, I keep seeing you say EMS, is that Eternal Mangekyo Sharingan?