Babidi was determined to resurrect Majin Buu so that he could continue his father's work, namely conquering the universe, and thus make him proud.

Spoiler

Babidi took over the minds of Dabura, Pui Pui, Yakon, and Vegeta to help him in this cause. Babidi's mental abilities are very powerful, surpassing those of various mystical individuals who reside in Other World such as the telepathic North Kaio, and illusionist Princess Snake. After Buu is released, Vegeta nearly kills Babidi when trying to destroy Buu. When Buu is seemingly destroyed, Piccolo bisects Babidi and leaves him for dead. After Buu revives himself, he finds Babidi who then orders Buu to revive him. Babidi orders Buu to kill Dabura, Kaioshin, Gohan, Piccolo, Goten, Trunks, Vegeta (before his sacrifice) and whoever else stands in his way. As Buu is very disobedient, Babidi can only control him by threatening to seal him up. After an encounter with Super Saiyan 3 Goku, Buu learns that he is stronger than Babidi. Realizing this, Buu strangles Babidi (so Babidi can't say the spell to seal him up), and then punches his head off in rebellion. Babidi is seen in hell with Cell and Freeza but wanted the Z fighters to win after having created a grudge against Majin Buu.

Source - Wikipedia