Why Kesavanand Bharti Case of 1973 is famous?

Kesavananda Bharati v. The State of Kerala and Others (AIR 1973 SC 1461) is a landmark decision of the Supreme Court of India. It is the basis for the power of the Indian judiciary to review, and strike down, amendments to the Constitution of India passed by the Indian parliament which conflict with or seek to alter the constitution’s ‘basic structure’.
The judgment also defined the extent to which Parliament could restrict the right to property, in pursuit of land reform and the redistribution of large landholdings to cultivators, overruling previous decisions that suggested that the right to property could not be restricted. The case was a culmination of a series of cases relating to limitations to the power to amend the Indian constitution.
The 42nd amendment is thought to be the immediate and most direct fall out of the judgement. Apart from it, the judgement cleared the deck for complete legislative authority to amend any part of the constitution except when the amendments are not in consonance with the basic features of the constitution.
The basic structure doctrine is the judge-made principle that certain features of the Constitution of India are beyond the limit of the powers of amendment of the Indian Parliament. The doctrine, which was first expressed by the Indian Supreme Court in Kesavananda Bharati v. State of Kerala (1973), reflects judicial concern at the perceived threat to the liberal constitutional order posed by the Indian National Congress’ majority in central and state legislatures, in particular under Indira Gandhi.
The basic structure doctrine applies only to the constitutionality of amendments and not to ordinary Acts of Parliament, which must conform to the entirety of the Constitution and not just to its basic structure.