Extremist idealogies can remove the often immense pressure involved in taking various issues as stand alone matters that have to each be thought out in a factual manner. The polarization inherent to ideological extremism leads to groups of people with mutually affirmed beliefs. The pressure of thinking about each issue that arises in an individual manner gives way to pre-prescribed thinking that follows the party line so to speak.
Extremist positions have a tendency to assign binary solutions to perceived issues regardless of said issues complexity. The reality is that complex issues especially those involving politics, social issues, science (especially climate science) or ethics rarely have simple binary solutions. By adopting extremist positions one can defer to a polarized binary solution. Extremist views when they are supported by a sizable group of peers can provide comfort in what can often be a bewildering and frightening world.

I think it has something to do with tribalism.

Read “True Believer” by Eric Hoffer

Been hearing a lot of comparisons between progressive ideology and religion. It makes some sense that people crave something to point to as a stable basis for moral values to live by and without a religious base to lean on they find political ideologies. Which leads me to conclude that the rise in extreme ideology is an extension of the need to belong to the most popular or extreme parts. Just look and some the most famous televangelists. Most are bst crazy but still draw hugh followings.

I suspect mass hysteria plays a part in that...

Simplicity. And laziness. Having to think for oneself is difficult and not very socially acceptable. Realizing that complex problems demand multifaceted solutions can be stressful. Much easier to have someone else tell us what to think and it is really easy (as we all have experienced) to be manipulated by our outrage. ...And then there is this: ``Reason is poor propaganda when opposed by the yammering, unceasing lies of shrewd and evil and self-serving men. The little man has no way to judge and the shoddy lies are packaged more attractively.'' - Robert Heinlein, Assignment In Eternity,

they havent read ayn rand or subscribed to jordan peterson's self authoring program(low monthly payments).