It is called as Search Engine Optimization (SEO). It depends on many factors. Keywords, backlinks, etc. Maybe CoinDesk concentrated on their SEO? Or as the other user pointed out, results might be tailor-made based on your recent search/browsing history. When I Google 'bitcoin' bitcoin.org is the first result.
yep google pays attention to where you go "in life and on the web" and tailors searches to the person, and advertisements always go up front of line followed by what google thinks is what you first wanted... wikipedia i think is best :-)