I'm not too proud to admit I had no idea this was even something I should have been worrying about all this time.
Catching up, the story seems pretty clear cut. The government wanted to build a road (either because one was necessary or, as some argue, because it was a useful, economically hopeful political ploy) through an area that is teeming with amazing life, some of which tends to move through the area in massive herds.
What's weird is that it appears as though the government actually listened to the objections of scientists in deciding to prioritize the ecological well-being of the Serengeti. Or else maybe it was the argument that the damage the highway would do to the tourist industry in Tanzania would outweigh any economic benefits the highway would bring.