These days, the major news corporations are so extensively saturated. It is 24/7/365 and on TV, computer, mobile, radio and print. They care for viewing figures and their own publicity. They aim to inform, educate and crucially to entertain and they succeed in those three aims when something like the recent attacks occurs. In a developed country, with high security and a stable and prosperous population. Security and stability were compromised in a rare act of violence (relatively speaking) and the media could focus on this so comprehensively because the communication networks are so active in European countries.
And then of course there's always the continued belief in the white man's superiority over the rest. While lives matter most :P