As a means to an end. He wanted Sasuke's body as well as revenge on Hiruzen, attacking the entire village and throwing it into chaos was an added bonus.
Because his parents get killed & he thought that it is because of village & Shinobi system that's y he became evil and it made him to goup against the village............
to get stronger by unlocking secret about powerful ninja so that he can improve is self to the most powerful and be immortal sasuke was just a extension of is life span. he keep on taking DNA of powerful ninja to put in is body
Jiraiya said that he believed that Oro's obsession with forbidden arts came as a result of his parent's death and that he blamed the village for their demise.