Why are State Legislative Assemblies involved in the election of the President but excluded from the process of impeachment?

Article 54, 55. Indian Constitution talks of appointment of President of India. Election of President: Electoral college consisting of elected MPs of Parliament and elected MLAs of State Legislative Assemblies. Proportional representation + Secret Ballot + Single Transferable Vote. Impeachment involves: 2/3rd of Total Members of both houses. State Assemblies are excluded because: 1) Will make the process complex 2) Instability could arise in part of President because state could get 2/3rd majority collectively having Parliament without any law 3) Imposition of Presidential Rule in states could cause issues 4) But also included in election because Federal, unity and voice; President empowers Head of State comprises Union and state. Moreover, President's role in maintaining unity among state and Union is of paramount substance.

Will insure political constellation at local level. Populist agendas. Instability could arise in part of President because states could get 2/3rd majority collectively having Parliament without any law. Imposition of Presidential Rule in status could cause issue.