It's common here to criticize Great Man Theory, in that it's not just one person that caused changes, it's many. However, where I'm lost is where they further imply that things happening have absolutely nothing to do with individual choice, and material conditions are the only thing that matters. This really just sounds like predestination with extra steps, as in, your material conditions will choose whatever actions you take, which completely loses me.
The logical conclusion to this mindset is that organization and trying to do political action is pointless, after all, material conditions will either make it happen or not make it happen, which I don't think anyone is trying to say.
Free will might not exist but you've lived plenty of your life without it already and you didn't even notice. Just keep trucking and keep up the good fight comrade. The material conditions you've experienced in your life up to this moment will determine whether you're the type of person who learns this sort of truth and descends into nihilism or whether you're the type of person that embraces that knowledge and continues to act anyway. In either instance though you as an individual are incapable of grasping those conditions clearly enough to know that answer until it's behind you. That critical lack of knowledge, a lack of omnipotence, is what you experience as free will in that you can't know what all the possible outcomes are so you as the individual have to choose as if you are truly free