William McKinley was not a warmonger. He was a Civil War veteran, so he was familiar with the face of battle. But the pressure to do something became too great after the Maine blew up, and war became inevitable.
The war started as an effort to address Spanish human rights violations in Cuba, a rationale that would have been more familiar in the next century. It ended, however, as an exercise in American imperialism. America would use its naval and financial power to get its way in its backyard for decades to come. Does that sound at all familiar to you?