90% done with The Brothers Karamazov

So why does Smerdyakov kill himself (and Fyodor)? We get a lot of talk all through the novel about how Smerdyakov is a terrible person (stinking, as his name suggests), but isn’t he the most in need of pity? The only person who seemed to show him any respect was, ironically, Fyodor (trusted with the money, sent him to school, told him the knocks). Doesn’t his suicide (off-stage, too) show him miserable and lonely?