I think it's pretty obvious.
Voldemort has always been attracted to power, and it's well known that Hermione is the most powerful witch of her generation.
He made several overtures to her, but was unable to turn her from her path, and so he killed her.
Upon her death he felt great remorse (such was his passion) and decided to bring her back from the dead (such was his power).
Dumbledore tried to stop him, and so was eliminated.
In fact, Voldemort was so enamored of Hermione, that after she was brought back, he use dark magics to give her even greater power.
Quirrell (who has been hiding his identity of David Monroe) was secretly on hand for the ceremony, but by the time he realized what was happening, it was too late to stop it.
Cutting charms were used on Voldemort's hands, and other terrible damage, but despite all this, Quirrell was defeated.
Ironically, having given her the power of friendship, it was the power of friendship which ultimately was his downfall.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 116.
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)