You have posted contradictory information. Your first quote (that you didn't link to, I will here) states that 50 million copies were sold by 2003. Your second quote (source because you were too lazy) repeats the figures given by the director of publishing at HarperCollins, which are that 100 million copies were sold before the films were released.
But even if it were true that 'only' 50 million were sold before the 2001 film, you originally stated that "the movies were what made the series popular", and I would argue that sales of 50 million are quite enough to qualify the series as being popular.
I'm not going to keep responding to this particular issue as it's off-topic.