why was the necessity of getting a construction formulated by a popularly elected constituent assembly felt after second popular movement 2062/63? list reasons

The answer is "nativist" approach. 

Noam Chomsky is the primary scholar related with the nativist point of view. The nativist theory is a theory which is based on the biological structures, which contends that people are pre-customized with the inborn capacity to develop dialect. Noam Chomsky built up the idea of the Language Acquisition Device (LAD).