If the blacks had been driven to Africa, American history would have been different, many of them unintended consequences but there's no reason to think that anyone behind segregation was thinking that far ahead when they set it up, for whatever reason they set it up.
It's just ludicrous to think that was the reason they came up with segregation. If they wanted blacks to go to Africa, they would have offered programs where they could work for their passage 'back.'
Or they should have briefed judges, 'don't keep giving civil rights to the Negroes, we're trying to get them to move back to a country they've never seen, but we're not telling them so they'll think it's their idea.'