The bad spelling, the claiming to be from Nigeria thing, this is suppose to reduce false-positives. The last thing they want are people who are fooled enough by the well done font and professional looking design and the seemingly legit promises to respond initially and then take up their very real time and then balk at the part where you wire money to Nigeria. It turns out if you make it obvious, only the very very stupid will respond, and that's exactly the target demographic.
Wow. I wouldn't have thought of that.