Why did the bourgeoisie of the North compromise with the former slave owners?

Despite the fact that the civil war was started under the slogan of freeing blacks from slavery, its main goal was to eliminate the competition of the bourgeoisie. The slave-owning South hindered and restrained the development of the capitalist North. As soon as the war was over, the slave owners were effectively removed from the political arena of the States and all the levers of power were in the hands of the bourgeoisie of the North. But at the end of the war, ordinary people, including former slaves, received more freedoms and the bourgeoisie found that they now have a strong opposition in the person of ordinary workers. That is why the bourgeoisie made concessions to the former slave owners – in order to conclude a class alliance and suppress the indignation of the Negro and farmer movement.