When a rebellion in Cuba against the Spanish started brewing, Hearst and Pulitzer saw a golden opportunity; they'd report on the situation in Cuba to sell papers, and if the situation wasn't interesting, they'd make shit up because journalism is easy when you don't have a soul. Hearst and Pulitzer would take sensationalized, unverified stories of made-up atrocities, make those stories even more sensationalized and then feed the twice-baked-sensationalizations to the American people as the truth. And the people, thanks to the papers, believed that America had an ethical obligation to step in and save those Cubans.
Every John Q. Public with a paper assumed that the Spanish warlords were raping and murdering the poor, defenseless Cubans and leaving them in rotting piles on the side of the road, because that's the kind of story you write when you own a newspaper and are bored. When a Journal news photographer attempted to leave Cuba, reporting to Hearst that the situation wasn't as bad as Hearst had reported, Hearst sent a cable boasting, "Please remain. You furnish the pictures, I'll furnish the war." Then the USS Maine, an American warship, blew the fuck up under questionable circumstances.
Post-explosion, President McKinley demanded an immediate investigation, but Hearst and Pulitzer demanded even more immediate "THE SPANISH DID IT" headlines. Their reporting was so immediate, in fact, that word had reached the American people about Spain's involvement in the sinking before the investigation even started. To this day, we don't know why exactly the Maine exploded, we just know why it didn't: the Spanish. But that didn't get in the way of headlines! What a scoop!
in 1976, Admiral Hyman Rickover, father of the nuclear navy, conducted an investigation and concluded that Spain was blameless in the explosion that sank the USS Maine. This was a posthumous vindication for the commander of the Maine, Captain Sigsbee, who had said the same thing only to be excoriated by Pulitzer and Hearst for "failing to see the obvious."
The US went to war over Pulitzer and Hearst's circulation-building stunt.