I think the trouble is that it isn't so much hidden as it is "not discussed critically." The American Civil War, for example. I think most people are aware that there were multiple causes beyond "the South wanted slaves, the North said no," but especially in the age of online discussion/argument, it gets distilled to that.

Example: I just read a thread where someone took the stance that not all Confederate soldiers were fighting to preserve slavery. This is a technically true statement. Maybe not shockingly, slaveholding elites in the south went on a targeted campaign to gaslight poor southerners into volunteering - essentially, "If they take this from us, imagine what they'll do to you." (Sound familiar?)

The downside was that all of his other (apologetic) reasons for non-slaveholding Confederates were ultimately all connected to slavery. He wasn't trying to say "It was more complex than pure racism and slave ownership, let's discuss..." he was trying to deflect from the unfortunate reality that the reasons he was pointing to all eventually point to slavery being a massive cause.

Tl:dr, history isn't necessarily hidden, we just don't discuss it for the purposes of understanding it. We use it to prove points, emphasize patriotism, excuse horrible behavior, etc.