Even though this is just a miniseries, it's already straining to keep the drama going. The scene with the Booth brothers really highlights the problem. The dynamics between those two suggest a more interesting story they could have told.
They're trying to tell the story of how the Confederacy attempted to survive Appomattox, but it's being told via Wall Street bankers and foreign interests who want the cotton wealth to keep flowing.
People trying to make money just isn't an interesting psychological motivation for a story, not unless there's something else in it. But the rivalry between the Booth brothers, which contributed to John Wilkes' attempts to be a showy "hero" and outshine his brother, is far more engaging.
The story with Mary teaching freed slave children to read is nice, but what does it have to do with the core story at all? Seems shoehorned in. I'm trying to figure out why they made her a major character in this story.