Spinoza argues that when you understand reality fully, you love it. But what do you do when you understand reality and it doesn't make you happy at all?
Spinoza believes that adequate understanding necessarily increases our power to act and therefore tends toward joy. But this depends on an assumption that he never really proves. He assumes that confusion is the main source of suffering and that understanding dissolves confusion.
Sometimes that is true. If I understand why an eclipse occurs, I no longer fear that a dragon is eating the Sun. Understanding has removed unnecessary fear. If I understand why someone insulted me, I may stop taking it personally. Again, understanding reduces suffering.
But now consider your example. You understand evolution. You understand predation. You understand that wolves did not choose cruelty in a moral sense. You understand that concentration camps emerged from historical, psychological, political, and biological causes. Your understanding is deeper than before. Has the suffering disappeared? No. Why? Because the suffering no longer comes from confusion. It comes from accurately perceiving what reality contains. This is something Spinoza does not sufficiently distinguish.
There are at least two kinds of suffering. One comes from false beliefs and confusion. The other comes from contact with reality itself. Understanding can eliminate the first. It cannot eliminate the second. In fact, it can intensify it. The better an oncologist understands cancer, the more clearly she sees its devastation. The better a historian understands genocide, the less able he is to dismiss it as an accident. The better you understand trauma, the more you realize how profoundly a child's nervous system can be shaped by people who were supposed to protect it. Knowledge has not failed. It has revealed reality more accurately.
Now consider this sentence, I have a different nervous system, already altered by trauma from the people closest to me. I understand reality but I suffer. That changes everything. Spinoza tends to treat adequate understanding as though it acts directly on the emotions. Modern neuroscience would say the relationship is much more complicated. A traumatized nervous system does not merely contain false ideas. It contains altered threat prediction, altered stress regulation, altered autonomic responses, altered expectations of other people, altered bodily states. Spinoza couldn't include these.
You can understand perfectly that someone is safe and still feel fear. That is not because your understanding is inadequate but because different learning systems are operating. This is one place where modern neuroscience genuinely extends Spinoza. Understanding is one causal force among many. It is not the only one.
You can claim that : The more I understand this, the more I suffer. That sentence is only half complete. Could it perhaps be, The more I understand, the less I hate reality, but the more I grieve what reality contains. Those are different emotions. Hatred says, "This should not exist." Grief says, "This exists, and it is terrible." Spinoza sometimes seems to expect that understanding should transform grief into joy. That expectation asks too much of the human nervous system. A nervous system capable of attachment will grieve. A nervous system capable of empathy will suffer when another creature suffers. That is not necessarily an error. It itself is part of reality.
Perhaps the deepest understanding we can offer Spinoza is that adequate understanding does not guarantee happiness. It guarantees that our suffering becomes increasingly about reality rather than illusion. That is a humbler claim, but truer.
If you want to come closer to reality, not farther from it, so the cost of that project is that reality contains wolves, warthogs, trauma, aging, entropy, and death. No philosophy worthy of the name should promise that seeing these things clearly will make them beautiful. What it can offer is something different. It can help us stop wasting energy fighting illusions so that whatever strength remains can be directed toward responding to the real conditions of life. That is a quieter achievement than Spinoza's promise of joy, but it is one that many people, especially those who have lived through trauma, may find more faithful to experience.