Beyond the obvious examples like Buttigieg.
Imagine being one of the most influential American Marxists of the twentieth century, then having your son get a job at the Soros foundation, then he later writes a hagiography for fucking Alexander Hamilton
Why can't it be both material conditions and theory? Some people hate their jobs but literally don't have the vocabulary to think outside the box of capitalism.
It's both and I should've said primarily in the title.
I do think that one's class interests generally create the window of what politics someone finds acceptable, but you're right in that Theory is still instrumental in allowing people to realize their class interests, and shaping someones politics within that window.
Something something liberatory education something