Nigeria now ranks as the fifth-largest
country in the world and number
one in Africa for Opera Mini browser
usage, surpassing other
technology-savvy countries like
China, the United States and Brazil,
the company has said in a press
release.
The report, which revealed the top
four sites for Nigerian mobile surfers
to be Facebook, Google, Yahoo!, and
the BBC, also shows that Nigerians
now engage in more data services
with 90 percent of mobile surfing
done using Opera Mini.
The company say the flexibility of
the mobile browser, adapting to
more than 3,000 different mobile-
phone models, from basic feature
phones to the latest smartphones
has also accounted for the surge in
the mobile web users, which is
responsible for the 73 percent of all
mobile web users in Africa.

Nigeria population is advantage here.

I doubt that.  Most mobile web users are students and most are free one OPERA MINI. Nigerians love free things.

To some extend you are correct, speacially in  the area of liking free things, not peculiar to Nigeria though.