I really do not think we are going to get to any causal relationship here. One thing you might want to consider is the link between IQ and politics.

Smart people (generally) tend to be more liberal:
https://theconversation.com/do-smart-people-tend-to-be-more-liberal-yes-but-it-doesnt-mean-all-conservatives-are-stupid-57713

Childhood IQ in Britain, for a 1970s cohort, predicts voting for more liberal parties (Greens and Lib Dems):
https://www.research.ed.ac.uk/portal/files/8896159/childhood_intelligence_predicts_voter.pdf

This answer is only meant as a starting point. You would need to consider all of the evidence from across the world (perhaps the reverse is true, in general, for example. And perhaps other variables come into play).