IIITs and IISERs: Why?

Here's something I don't get:

We have 25 IIITs (institutes of information technology). Most of them offer programs in only two disciplines: Computer Science and Electrical Engineering. Just two.

A few of them are IIITDMs (design and manufacturing added) and these additionally offer programs in mechanical engineering. That's three disciplines.

And all these IIITs and IIITDMs have needed substantial real estate and infrastructure investments! 

Now, we already had so many IITs and NITs that are full blown institutes with pretty much all science and technology departments. Why were seats simply not increased as needed in CS, EE and ME in these institutes, more faculty hired and classrooms and labs expanded? We would have achieved the same results with much much much lesser investment. And the crores and crores of rupees saved could have been utilised to address other needs.

Likewise for IISERs: Science departments in IITs and NITs could have been expanded - and the institutes renamed to IISTs and NISTs to lay an equal emphasis on Science and Technology - instead of bringing up entire institutes that only offer science programs. 

We would have saved thousands of crores of rupees.

Plus students would have had a wider range of electives to choose from and a broader exposure to research labs cutting across disciplines.

Where's the thought process behind decision making?