It might mean a lack of 'exemption from punishment' for the the people partaking in violating human rights.
As in the military tends to forgive less and punish the people more for violating human rights. I.e; lack of forgiveness.
According to Oxford dictionaries, the derivation of disappoint is -
late Middle English (in the sense ‘deprive of a position’).
So I suppose the meaning of disappointment has extended over the centuries from the feelings of someone who didn't get a job they had wanted, to cover all kinds of disappointment. People sometimes amuse themselves by thinking of ...
"Never managed to do it again" implies some sort of "doneness," i.e. one has given up trying to do it again. This tense is called the preterite. The focus is on the action (in this case, the failure to make fire again).
"Have never managed to do it again" implies some sort of continuity, i.e. one is still trying. This tense is ...