The author and the date are both significant: Khomeini went far further than most of the religious leadership in his opposition to the Shah's personal rule, and here he's simultaneously proclaiming the illegitimacy of the then regime and the need for clerical leadership of a new state. It's really the moment when the outlines of the post-1979 order are first laid out.

But it wasn't always always thus: the clergy had held the Safavid dynasty in high regard (reciprocating its promotion of clerical authority), and even after viewing its successors as usurpers, senior religious figures made their peace with the Shah after the 1953 coup before their falling-out in the 1960s gave the already outspoken Khomeini his opportunity to claim spiritual leadership of the opposition movement.

Nor was Khomeini's authoritarian clericalist take characteristic of past anti-regime religious sentiment, senior religious figures often siding from the 1890s with popular protest movements (to some extent foreshadowing 1979) and being associated with the 1906-11 constitutionalist movement and (at least for a time) the parliamentary cause in the early 1950s. The republic's eventual form was in part a historical accident, Khomeini emerging just as an earlier generation of leaders was passing from the scene.