When the India-Pakistan war of 1947 was fought, although India and Pakistan were both brand-new independent states, it seems to me that Pakistan had much more serious disadvantages: they were a smaller state, governing two widely-separated noncontiguous territories, and (if I understand correctly), India enjoyed some British assistance whereas Pakistan did not.
Yet Pakistan managed to hold onto one third of Kashmir. Why didn't India curb-stomp Pakistan?
Several reasons. Firstly, to be blunt, both militaries were not very proficient fighting forces by any stretch of the imagination. Additionally, Pakistan made very good use of unconventional forces that got behind Indian lines, making things even more difficult for the Indians. However, the main problem for India was the UN. In the long run, India's superior resources probably could have, like you said, curb-stomped Pakistan, but before they could do this, the UN mandated a ceasefire. Remember this is 1947, the UN is in its infancy and has a lot to prove. They do not want to become another League of Nations. As a result, they step in and force an end to the conflict.