Did environmentalists "trust" Al Gore in 2000? I don't know. None of us can read minds. The only question we can answer conclusively is, did Al Gore's environmental record harm him in 2000? The answer is no. See the post above.
The Greens may have hated Al Gore in 2000 but the truth is, they hated George Dubya more. The election did not turn on their votes. The numbers prove it. Argue with the numbers if you don't like the truth.