Why?
Declining birthrates.
The Left saw the numbers and knew that the aging workforce would be retiring and drawing government pensions that the rising generations could not support.
Answer to the problem immigration from nations with high birthrates and high unemployment.
Their multiculturalist views precluded them from realizing that these people from a radically different culture would be the source of an existential threat to their society.
And their multicultural views would also prevent them from dealing with the problem when it actually revealed itself in all of its bloody reality.
Hopefully the immigrant population has not reached critical mass where it’s too late to roll back.
This year will tell a lot.