Seems to me like an attempt to further the Orwellian decline of language accepted by the public at large. First they get us to dehumanize people by calling them terrorists. Then they get us to buy a “War on Terror”, as if that made any sense or could ever end. We also had an “Axis of Evil” and “Patriot Acts” – that seemed to fly with many people, getting people behind tossing our rights and forming secret courts, and a new department of Homeland Security (that’s practically what Gestapo means in 1940s German, Geheime Staatspolizei – homeland state police, by the way), supposedly in order to defend our rights because “they hate our freedom and our way of life” (LOL), and of course invasion of Iraq, drone strikes, etc. The word “radical” is used as another way to shift our symbolic thinking to an “us versus them” mindset. Pretty much anyone speaking the truth against the mainstream corporate machine is also termed “radical” or “extremist”. “Radicalization” is used in a way that makes it sound a bit like a disease or zombie outbreak, to further stoke fear and dehumanization and so foster acceptance of suspending usual laws and restraint in favor of taking action to stop those scary radicalized terrorists… and perhaps distract from noticing how ISIS and Osama were to some degree made what they are by the US, and the other reasons why these people are choosing violence and martyrdom.
By pretending it’s meaningful, important and correct to frame the question (of why people are being violent in these ways) as “are they self-radicalized or not?”, it avoids other questions and makes it sound like the official approved mindset is a matter of significant fact, and that that’s all there is to it, and that thinking need not go further. It’s also a way to point fingers at the next target you’d like to invade or attack or threaten. If you can get people to buy that the bad guys were radicalized by your next target of choice, you can try to sell that as a reason to fear them and so strike first. e.g. Part of the argument to invade Iraq was about them having “terrorist training camps”.