There are several distinct genetic lines in India. Like China or Russia they are not a singular genetic branch of humanity. The successful lines of India have Aryan bloodlines. Which is why they are today part of the Aryan stock - like it or not. Even Hitler recognized their ancient ancestry and associated intellectual prowess among these blood lines. The Aryans established their entire caste system which was largely driven by their genetic ties to the Aryans. The more Aryan blood you have the higher in the system you rank. Of course, that steadily changed over time and especially modern day. These ancient Aryan bloodlines have created some very smart Indians which are not necessarily indicative of the average Indian citizen. For example, in America, White males pay most taxes (roughly 80%). The second largest group is Indian males. A small subset of Indians with Aryan blood ties are capable of intellectual endeavors. As others point out, nuclear technology is well documented and not difficult to do. Just about anyone with an IQ of 125 or higher can successfully create a nuclear weapon. It may not be particularly efficient but the technology isn't so hard as often presented. For example, if you create a 50MT nuke and you yield 15MT, does it still count as a nuke? Add to this there has been a black market for scientific expertise since the 1950s. Consultants can easily improve that 15 back to 50.