Gore used to be this benign, blue-collar Democrat - I mean he was the perfect moderate Democrat.
I think losing that election to Bush really caused something in his to snap. He's always championed the environment, but throughout the 2000s, he just became this grotesque, bloated figure preaching doomsday.
No wonder why Tipper divorced him after 29 years
This appears to have happened around the same time:
https://slate.com/human-interest/2010/07/why-the-masseuse-s-story-about-al-gore-rings-true.html