Moore announced her intention to divorce Kutcher earlier this month, stating that she "holds certain values sacred" which were not being honoured in their marriage.
According to People, the relationship between the couple "[had] been deteriorating for a long time".
A source told the publication: "Ashton was ready to end it, [but] he wanted to wait for Demi to actually do it. He loved her but couldn't live with her."
While Moore was said to be dedicated to saving their marriage, she was apparently unable to cope with the allegations that Kutcher had been unfaithful.
"[She] really wanted to save the marriage but couldn't deal with the pain of his cheating," the source added.
Moore was said to be feeling 'fragile and alone' following the split, fleeing to Hawaii to be away from the press.