Word for "extremified"?

I tried to describe something I read on the phenomenon that views in groups invariably shift toward the more extreme of the individuals and their group average, so to speak. Therefore there views were [extremified].

In the comments, Hugh suggested the word polarize, and Hot Licks suggested the word radicalize. I agree with you that both suggestions apply to the situation that you describe in the question. These words are often used together.

They have somewhat different meanings. Polarization implies the development of opposing extremes (for example, someone might lament the "polarization of politics" in the context of the two-party system of the USA) and the reduction or elimination of intermediate positions between these extremes. *Radicalization" refers to a shift away from mainstream or moderate viewpoints.