He was asked by Schwarzenegger for advice on California economic policy. Warren did his research, and astutely suggested they should try to scrap Proposition 13 (IMO it's among California's worst policies, but it's a political third rail). I don't think he was asked for economic policy advice ever again :)

I'm sure he's full of good ideas. I think they were just a bit more ambitious than the last 40 years of politicians were willing to stomach or advocate for.