Why the India adopted multi party system explains
Answers
So, let me explain to you with an example.
This is for conceptual understanding. If you're wanting a more "exam oriented" answer, please continue reading this and I'll tell you.
Let's say that you are the new student in your class. You want your classmates to like you and respect you. Hence, what do you do?
You go to each group and introduce yourself. You give everyone a chance to talk about what they like and dislike. Hence you can learn about their interests and fit in easily.
Coming back to the point,
India has a multi party system because of its diverse culture and representation. Not all the population are Hindus. And not everyone have a common mindset about things.
Hence, India needs a multi party system for equal representation of the diverse ethnic groups and to encourage popular opinion.
Why can't India have a bi-party system like in America?
This is due to the same mentioned diverse cultural groups. America also has a lot of ethnicity, but not as diverse as our country. And it is important, as stated by our constitution, to grant freedom to citizens as per the fundamental rights - Freedom of Speech and Expression.
Hence, India has a bi party system because the Constitution encourages equality in representation.
Why can't India have only one party?
Then that means that India is a democracy which prohibits the voice of the people. People will not have different choices and different candidates to choose from.
Hence, India has a multiparty system to encourage people's participation in democracy and new ideologies to come up.
These are the main reasons why we chose multiparty systems.