Did people lose hope because things weren't changing or was it a malicious effort by white America?
Do you mean the Black Power movement/militant Black power, such as the Black Panthers? And I would not say that black pride has died in the U.S. I'm not sure where you're getting that from
You supposition based on the twenty year rule is that black power/black pride declined from some high point prior to 1995. When do you believe the high point of black power and black pride was and what fuels your belief the decline occurred. Can you restate your question in a way that makes your hypothesis clearer.