Why does Oberon cure Titania of her infatuation with Bottom in A Midsummer Night's Dream?

Oberon had Puck annoint Titania's eyes because he wanted
to make her look foolish as she fell in love with whomever or whatever she saw upon
waking.  He got his wish when she awoke and saw Bottom with his ass's head, then
promptly fell in love with him.  Oberon wanted Titania to look foolish because he was
angry with her when she wouldn't give up the changeling child who was currently
receiving all her attention.  Titania said the child had belonged to a votress of hers
(a lady in waiting) who died and upon the lady's death had promised to care for the
child.  Oberon was jealous of the attention the child was getting and he wanted Titania
to give over the child to him, but she refused.  Oberon figured that if Titania's
attention was distracted by being in love, he could get the child from her and his plan
worked.  Since Oberon had the changeling child, he no longer needed Titania to be in
love with Bottom, so he annointed Titania's eyes again and when she awoke, it was Oberon
that Titania saw.  Their relationship was once again loving.