so India is a federal state, which means that it has multiple levels of government-centre, state and local government.
There are a couple of reasons for this:
Our massive population
A country which houses over a billion people CANNOT be managed by one government. More the people, more the number of problems. And to address them, we need multiple levels of government.
2. Diversity in our population
India is probably the most diverse country when it comes to religion and culture. To manage this diversity, we need people who understand our issues. And one prime minister/few cabinet ministers JUST CANNOT cater to the needs of a country this diverse.
3. The demograhy of our country
In India, over 68% of people live in villages. So, it is quite obvious that we need a government at the village level too. Considering this, our lawmakers made PANCHAYATI RAJ compulsory in the 42nd amendment of the Indian Constitution in the year 1992.