Why were land ownership and education so important to freed African Americans?

Essentially the same reason these things are important to anyone, that land ownership gives a sense of self-worth and stability, and that education enables one to improve oneself intellectually and materially. These things were so important to the freed slaves after the War of Secession because these were the things that had been most denied to slaves.  There was a large population of free black landowners in the South before the war, but to the former slaves this was the first step to equality with both the earlier free blacks and with white citizens.  Education meant that the next generation could improve its lot.  The first generation of freed slaves might be farm laborers and small landowners, the next could be larger farmers and teachers and clerks, the next could be doctors, lawyers, businessmen and artists.

The necessity of this was borne home to the freed African-Americans because of the social situation at the end of the war.  The causes of the war had largely revolved around tariff legislation, economic exploitation of the South by industrial interests in the North and other economic and political issues.  Slavery had been a minor cause of the war itself, although it was the most glaring example of America's failure to fulfill the ideals of the Revolution.  As the war progressed and the Union needed a moral issue to keep morale up, slavery (in Lincoln's speech after the Battle of Antietam, or Sharpsburg) became that issue.

So, at the end of the war, slaves were freed, but the promised "40 acres and a mule" from the government did not appear, and so there were thousands of homeless blacks wandering around the South, the region completely destroyed, and all the whites being told that this devastation had been for the benefit of the blacks.  Obviously, this caused problems, and racism became worse as time went by, peaking between 1890 and the late 1920s.  Land ownership and education became the single most important thing to blacks in this environment, and stayed so through the Civil Rights movement post-WW II.