Why so much interest today in an obscure and ancient philosophical question?
Of course the negation of free will is vaguely part of Marxism. The collapse of capitalism is predetermined no matter what the participants want. It’s “You didn’t build that.” It’s “the root cause of crime”.
But the best part of the pro determinism frame for leftists is the attack on objective reality and knowledge of objective reality.
They say that what you believe about objective reality is simply an adaptive evolutionary fiction that increases your chances of survival. You know nothing about reality; you know only representations that are useful to you.
If you claim that even if you are on the wrong side of history, you are nonetheless on the right side of reality. They can respond that there is no knowing reality. If you claim that men and women are different and you can support that by the number of hours worked or choice of occupations. They respond that your evidence is only belief in a manufactured “reality” that forwards your survival prospects.
Of course, since people do have beliefs they are quick to attribute beliefs to social influence. All beliefs are malleable, the ones you subscribe to now are a reflection of a certain societal power structure. If women had more power their choice of occupations would mirror men and their hours worked would be statistically identical to those of men.
The one belief that is not doubted is the belief in their theory of beliefs. There, they are correct. It is not a group of leftists seeking to influence fellow citizens and policy for their own self preservation. It is observation and reason proving that observation and reason cannot prove anything. Science proves that science is meaningless.
Wishful thinking finally is the final determinant of what we should do.