After Gatsby's death, why did Nick feel 'responsible' for getting someone for Gatsby?

Nick felt responsible because no one else was interested or willing....

At first I was surprised and confused; then, as he lay in his house and didn’t move or breathe or speak, hour upon hour, it grew upon me that I was responsible, because no one else was interested — interested, I mean, with that intense personal interest to which every one has some vague right at the end.