One suspects there's a lot less going on than what everyone would like to think. (Thanks, ChuckMcM, for the nice post about money and stock.)
Mr Cheever is "something of a product design genius, and lots of people give him credit for Facebook's best features;" even the now-removed-from-Quora post says "to him the user came first and growth features would sacrifice that." That puts him in complete opposition to the guy (Mr D'Angelo, who to his credit is putting his money where his mouth is) who is paying the bills.
The problem is that almost every Q&A type site has the same issue as Quora: only a small percentage of its membership is actively engaged. The number cited by the article is eight per cent, and in my experience, that's about par for the course. Since revenues (and therefore stock performance) are directly tied to use, there are two ways to increase revenues, with implications regarding the user experience for both:
1. Increase traffic, AKA "make the pie bigger". This means doing the kinds of things Mr D'Angelo probably championed -- the SEO Solution, playing nice with Google, low barriers to entry (i.e. Free). This is the tactic taken by most startups, since they're generally looking at Mountain View and saying "Gee, if we could just get our hands wet in THAT revenue stream, we'd be rich."
2. Keep your existing userbase more engaged, AKA "get your customers to eat more pie". This means doing the kinds of things Mr Cheever championed -- making the experience better, providing more services to them, concentrating on getting lifelong customers rather than more customers for less time. Most startups aren't in it for the long haul; they're in it for the big payday.
The NYTimes obit of Arthur Sulzberger pointed out the difference. His family has always wanted to be in the business of disseminating the news; their competitors are in the business of selling advertising. Mr Cheever wanted to take care of users; Mr D'Angelo wants to see a return on his investment. If there was ever a startup in the position to do the former, it's Quora; I know my colleagues would dearly love to have enough money to where they wouldn't have to worry for a while how to keep the lights on.
But as William F. Buckley noted a long time ago, "Idealism is fine, but as it approaches reality, the costs become prohibitive," and that's when someone like Mr Cheever moves on to his next venture.