When he was disguised as Madara, he would often tell stories from Madara's life or legends of the Sage of the Six Paths that had been passed down through the generations. Out of all of the stories about Uchiha Madara and the Sage of the Six Paths that he could have chosen from, the fact that he chose to tell these to Sasuke and Naruto and Kakashi is most telling.
When he had Sasuke captive, he had told him the story of how rather than having had his eyes stolen from him by a jealous and half mad older brother, Izuna had given his eyes to his more talented older brother so he could protect the clan. As his audience of Uchiha Sasuke remained captive, he'd told the related story of how Uchiha Madara had left Konoha, vowing to get his revenge. Uchiha Madara who had given his all, and who had sacrificed everything for his clan only to have them turn on him. When he had Naruto and Kakashi listening to him, he told the tale of the two brothers, the two sons of the Sage of the Six Paths, one who had been given everything by his father, and the other who had been completely disregarded even as the father lay dying.
Unfortunately, nobody had stopped to think about the stories they'd been told. Now, just as it had been then, nobody listened to Obito's excuses. Nobody could or would hear him despite the fact that he'd been standing there telling them "You betrayed me first.".