I think it's believed that the crime had to have been committed by more than one person
No; that theory is subscribed to almost exclusively by people who believe Knox and Sollecito are guilty. Knox and Sollecito's defense argued (almost certainly correctly) that Guédé acted alone.
See: You Be the Jury, The Amanda Knox Test
While we hear about Bayes' Theorem being under threat in some courts, it is nice to savor the occasional moment of rationality prevailing in the justice system, and of mistakes being corrected.
Congratulations to the Italian court system for successfully saying "Oops!"
Things go wrong in this world quite a bit, as we know. Sometimes it's appropriate to just say "hooray!" when they go right.
Discuss, or celebrate.