I think you missed OP's point. "Leads to" is the key phrase, and they're talking about how both ("Great Man" and "Inevitable Forces") theories end up being used

I think you missed OP's point. "Leads to" is the key phrase, and they're talking about how both ("Great Man" and "Inevitable Forces") theories end up being used as propaganda to support political purposes. Both (as you point out) have some truth to them, and (as you do) can be addressed objectively, but both can be transmuted into ideology,