When doing long-form videos, why do you create the landing page first before writing the script for congruency? Would it not be better to do it the other way around?

It doesn't really matter that much. The landing page is a foundational piece that will be there for a long time, and I want to get it done first because it has more of a tech load. Scripts don't always need to be congruent to your landing page. You can test different scripts to the same landing page.