U got that right, easy nuclear target are concentrated places like ISRO, BARC, HAL, etc. They never de-centralized because Nehru was so gullible and people from UP/Bihar were never so demanding as other states. They called Nehru as "Chacha" who literally screwed them over because of his ignorance of "smart" states who sucked all out of his hands. Now concentration of Idustries and R & D is a big problem when EU and USA are deconcentrating for security and other reasons.