Secondly, Obi-Wan was able to counter Anakin's attack from the lower ground because Anakin tried the same move Obi-Wan used against Darth Maul when Darth Maul had the high ground. Darth Maul literally just stood there and let himself get cut in half. Lightsaber duels (particularly in the prequels) are about pizazz, not realism. More @Wikipedia
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