The transition between the two occultations was managed, not sudden. During the lesser occultation, from 874 to 941, the hidden Imam was held to communicate through four men in succession, each recognized before the previous agent died and each serving as the sole channel for instructions and for questions put to the Imam, a structure that gave the community a visible, if narrow, line of authority even while the Imam himself was unseen. The fourth agent is reported to have announced, shortly before his death, that no successor would be appointed and that the greater occultation, without any intermediary at all, had begun.
That announcement closed one problem and opened a permanent one. With no agent and no visible Imam, Twelver Shiism needed some other way to determine religious obligation in his absence, and the institution that grew to fill the space is the marjaiyya, the practice of emulating a living jurist recognized by his peers as qualified to derive rulings, a role that carries real authority over ritual and legal questions but is explicitly understood as a substitute exercised only until the Imam's return, not a claim to his own protected status.
The absence of any living, reachable Imam also reshaped what a legal ruling could claim to be. A jurist's opinion, however well credentialed, remains explicitly provisional, always subject to correction should direct access to the Imam's own guidance ever become possible again, a qualification built into Twelver legal theory from the doctrine's own logic rather than added afterward as a hedge.