Aaj Ki Baat: Why did the Haryana chief minister change before election?

Today Naib Singh Saini took oath as the new Chief Minister of Haryana... Former Chief Minister Manohar Lal Khattar proposed the name of Naib Singh Saini as the leader of the legislative party... Saini is close to Khattar. ....is the President of Haryana BJP....currently BJP MP from Kurukshetra.