To be fair, this young DA never had a chance.
The Sheriff already went around him to bring charges without even consulting him. He had to establish just who was in charge. Had he decided not to procecute Kobe, he would have been run out of town on a rail. Even without bring the racial aspect into it, I get the impression that the people of that town do not like the aspect of a rich superstar athelete coming into their town and having his way with a member of their community, consentual or not.
I dont know if the DA had much of a choice not to prosecute, it may have come down to saving his own job. He chose wrongly, and if/when Kobe walks, he may as well pack his bags.