Most philosophers were BS rationalists trying to justify some irrational pet theory, not Spinoza. He was a pragmatist that cut straight to the heart of existence.

My take: Only at a high level of intellect are men free. The heart of animal existance is the ego emotional defense mechanism of which we creatues had no part of its design. It is not complicated. We creatures all are programed at the most basic level to want to seek advantage at every opportunity and live at all costs, and to often want to hide this impulse from others and even ourselves.