Because Victor Moses reckons he might not get in the England team, he has decided instead to play for the country of his birth which is what I'm pretty sure you are supposed to do anyway.
You may notice that in this picture Moses is wearing an England shirt and that is because until recently he really wanted to play for that country since he's lived there from the age of 11. International football used to be about the pride of playing for your nation, representing your country at the highest level and if you weren't good enough to cut it at for that team, you supported them instead. There are more important things than romance nowadays though, like money, so now that the young forward has worked out there's no way he's getting in England's World Cup 2014 squad he's decided to actually be very proud about being Nigerian.
It's sort of like that time I was trying to stop my friend from falling off a rope bridge over a massive canyon, but then I realised that I'd actually rather not have to work so hard and it was his own fault for being so stupid as to fall anyway. So I think he's dead now but also I think that might have been Cliffhanger I'm describing and not a real memory. Remembering things is hard.