Just so I can stop seeing Tobi is blah blah Izuna. Tobi is Obito because of the following:
1. He hints it in his own name.
2. His right eye is the eye that Kakashi didn’t take. If you are also thinking “Well Obito would have died”, that isn’t completely true. Tobi’s eye has the ability to suck up things and he can also retreat into it as well as teleport to other places via it’s use. So he could possibly sucked up the wreckage he was under when his ability was awaken or just teleported to another location while he was buried.
3. Tobi wants to end war so that must mean he was a victim of war. Now get this, what if what I said didn’t happen instantly? What if Obito was buried alive for a long long time? The amount of psychological damage that would of put on him would be to much for a mind to keep whatever morals he had before and could explain why he feels the way he feels. He survives then finds out that Rin is dead and the massive amounts of beef between the sides of the war he was in never got resolved. That would implore change right?
4. The time he attacked Minato would not put Obito at a young age. I’ve seen some say that Obito would be to young to attack Minato at that time. That’s not true. If you paid attention to the flash back then you would know Kakashi was very mature around that time and be in his later teenage/young adult years. Obito would be around the same.
5. Obito is no one. Just a corpse that did nothing significant but die just like every other ninja before him. He had no accomplishments. The only ones that could possibly mourn over his death or know he was are Kakashi, Rin, & Minato. Only one of those three are actually living.