By "intellectuals" the article is referring to professional intellectuals, e.g. college professors, pundits, think tanks, etc. -- people whose job is, essentially, just to be smart. Bill Gates, in managing a company, actually does something, and thus isn't in the group being referred to.

And if we speak of intellectuals who by choice labor hard in fields where the fruits are sparse, bringing them little monetary reward, should they blame those who attain greater harvest in more fertile fields?

Should they? No. But one of the points of the article is that they often do, or worse yet, blame the system that allows this to happen.