Where do you get that? Care to provide links which document or substantiate that?
They added that the pattern also suggests that people moving from moderate partisan counties are just as likely to move to extreme partisan counties as they are to move to other moderate counties. However, people who live in a politically extreme county are significantly likely to move to a similarly extreme county
Do people move because of their politics?
https://sciencenode.org/feature/Political%20Migration.php
AKA, Republicans fleeing California may move to conservative areas, but moderates move to conservative areas and vote “purple” or liberal.