I thought of Johnson being very much like Polk both Southern populist that served during the times of war.
Coming out of the Civil War the Union was very much divided and I thought of in terms of disenfranchisement of blacks that southern states other than Florida would have prevented black males from voting.
Also, why would Johnson win New Hampshire, New York, New Jersey, and Iowa. Those states hated him very much. Horatio Seymour only won New York and New Jersey in 1868 because he was Governor of New York, and besides, Seymour was nowhere near as racist and controversial as Johnson was.
Here is the clear answer - WEB Dubios has never had any logic when creating election what-if maps.