Why is this?
For some reason I have no problem "understanding" how someone born into wealth could nevertheless become a champagne liberal ("I never pretend to be one of the people, just to be for the people").
However, it's hard to "understand" the opposite.
How is it that people can come from hard or humble or "middle" class upbringing, yet become hard right, even ideologically rabid hard right? (I mean, apart from the misled religious hard-right.)
Supreme Court Justice Thomas comes to mind. He included in his life story a reference to his difficult formative years, with "there but for the grace of God go I"; but his ideological judicial opinions/philosophy is so contrary to that, it seems. Alito has a touch of it, in his hyper-rationalized world that seems out of sink with what one might expect given his background. Marco Rubio who embraces Arizona's show-your-papers law as "just" and not some ploy that doesn't solve anything. Boehner, this week, talking about how he worked every odd job he could find on the way up, now adamant about putting a tax-cut for the super-wealthy on the "national ATM" ...
Understanding the Joe-the-Plumber is perhaps easier.