To me it feels like a big grasp for meaning for many of the climate activists.

Without religion or kids giving a reason to live, mostly living for oneself is very depressive. (I know also people with kids do this)

Having a goal higher than yourself, especially that is of the highest moral purpose is very liberating.

It comes at a cost though, reason goes out of the window.

This doesn't mean there aren't real concern, but yeah the world is not ending.