In 1.3 billion people few may be interested in badminton or hockey but majority are interested in cricket only that's the prime reason BCCI has 38 domestic cricket team.. In last summer olympic, India won only one gold medal so you can easily imagine how much interest 1.3 billion have in other sports.
You can't measure the popularity of sport by looking in to the number of first class teams. In that case Australia is having only 6 first class sides, that take part in the Sheffield Shield. Now compare this with South Africa, where there are more than a dozen first class teams. But it is true that cricket is the most popular sport in South Asia (perhaps with the exception of Nepal and Bhutan). And I will not agree when you claim that popularity of cricket is the reason why South Asians are poor in other sports. Some ethnic and racial groups are superior in athletics and some others are not that good. Look at Jamaica. With a population of less than 3 million, they have won huge number of Olympic medals. And on the other side we have India. Population of 1.3 billion and in every edition of Olympics we finish behind Jamaica in terms of medal tally.