Because Modi is still elected representative as he has won fair elections. The problem in India is that the Opposition doesn't have any proper candidate. You are stuck between Modi or Rahul Gandhi who most of the public didn't like but opposition is not moving away from him because he is Great Grand son of First Indian Prime Minister, Grand Son of First female Prime Minister and Son of a Prime Minister. The whole Opposition party is surrounding only one family and the list of the Corruption that party did is way too long to write. I can confirm they are not winning in 2024 also as they have not learned a thing after 2 losses. It is kind of similar to US thing but if Both Candidates are not good But you have to elect one which is less problematic and will actually do some development. like Yeah Modi do have that hard Conservative ideas but he is best politician regarding infrastructure development for the country as the movement he has won the Infra projects are Getting fast and new projects are getting announced and completed. He is also good regarding welfare schemes.

And even if India is Multi party parliamentary Democracy only Two Big Parties BJP and Congress actually have chances of Forming governments. There is a 3rd party emerging in India Called AAP but it will take more than decade for them to be any threat to the BJP.

Modi party BJP got 37% vote in last election Congress 20% other 42% is distributed among different parties which then chose to form coalition between one of these two parties.

So even if the majority of the country is not voted for you the country has the first past post voting system you will win.

So Yeah conclusion is until and unless Opposition don't bring any good candidate and assure public there won't be any corruptions and they will focus on Their promises , Modi and BJP will be winning elections.