Because that spot at the south had Mt Kilimanjaro and Marble. I WANTED to settle the spot in the northeast first to prevent Shaka from grabbing it, but he grabbed it first.
Oh trust me, that was my first choice too. Shaka had it before I even got 3 pop in my capital. Then he settled another city right next to it so I didn't get any funny ideas. Knew I should've gone Liberty... not that it would've helped!
There really weren't any other spots left but Mt Kilimanjaro by the time I got my first settler out. I didn't want to settle in the desert where Nongoma was, since there weren't any luxes and one wheat is not enough food to grow, and Kwadukuza is next to a lux I already have. Shaka was gobbling up all the land northward, so I had to go south where there was enough food to grow an actual city.