What would you conclude upon reading the two clauses? Did Karen disappear because she wanted to disappear (e.g., go away on her own), or because of some other circumstances (e.g., she got murdered or whatever)? Or are both possible?
The context is from the book After The Storm in which Karen, who occasionally runs away from home and returns, this time, does not return.
Simply rephrasing it to "what led to Karen's disappearance" seems to be a much better, but does this change anything materially?