The most common factor that one can see in parts of India is that this country houses people of different cultures and one can easily lose track of the number of different languages that come out of a particular major language. So the major language is what is used as a common means of communication in those parts. The eastern part of India has large number of cultures residing and so it is quite natural for one to acknowledge the fact that this part also has a large number of languages is not going to strike one as a wonder. But the most followed language here is also the one with the most influential one as it has a very deep and rich history which connects to all who speak it. Yes, the reference is being made to the bangle language and this is the primary reason why the Bengali newspaper has a large circulation in this part.
Since the early days literature and art was very rich and keenly followed in Kolkata and so one can find that it could not have taken much time for this zest to flow towards newspapers. One of the first newspapers of India can b traced back to Bengal which goes as back as the 1780, so definitely they do have an upper hand which cannot be easily challenged. Then in 1818 the first Bengali newspaper came out and since then there has been no turning back and now is has evolved into a fully fledged industry with a large circulation.