India has long had a problem with it's defense industries, or companies trying to get into the defense business, over-promising. Actually, this is a problem in all industrialized nations. Defense work can be very profitable, and steady. But you have to do some, on the face of it, despicable things to get in. Promising more than you can deliver is a very common technique. That's because, when it comes to weapons development, this form of deceit works. The situation is worse in India because India has long prided itself as being a "non-aligned" (to any superpower) nation. Thus the idea of developing its own arms industries, to produce the most modern weapons, has great appeal. The politicians allowed themselves to believe the promises of the defense companies, that India could catch up, and compete with the leading players in this field. For the last few years, as one project after another was revealed as a pointless money pit for Indian made weapons that just wouldn't work, the mood changed. Blind nationalism, at least when it came to weapons manufacturing, was out. Pragmatism, and getting the stuff built on time, was in.
India apparently observed how the Chinese were doing it. In China, there was more emphasis on buying the scientific and manufacturing technology, learning how to master it, and then building the weapons. While this took longer, it built up China's manufacturing capabilities, and did not waste time and money on improbable weapons development projects. As India has demonstrated time and again over the last two decades, if you don't have proper technological capabilities, you'll never get your high tech weapons to work.
India has decided that it's more important to get it's Su-30 jet fighters fast, than to get them built mostly with Indian made parts. India has a technology licensing agreement with Russia, that not only allows India to build Su-30MKI fighters in India, but to manufacture most of the components as well. However, the Indian parts suppliers have not been able to get up to speed quickly enough to keep aircraft assembly going. India has a deal to manufacture 140 Su-30MKIs in the next eight years. By importing components from Russia, when Indian suppliers fail to meet their deadlines, the warplane production will stay on schedule.