This is a "Wild Mass Guess" entry, where we pull out all the sanity stops on theorizing. The regular entry on this topic is elsewhere. Please see this programme note.
The Lion King Adventures
It was all just a dream.
If you want to be boring about things, then the entire series could all just be a dream in Simba's imaginative little head, meaning that he never really did experience all that pain and tragedy. He never was a killer either.
Although this would raise questions about the quality of his mental health.