To take the position Imam himself did not make any effort.
Even five years before the event, Imam had necessary qualificatioins to be known as a Marja’ when he had finished his annotations on Urwat al-Wuthqa. The exposition he wrote later on Wasilah al-Nijah also added more weight to his scientific status.
In fact, after the demise of Ayatollah Boroujerdi prominent Islamic scholars elected Imam as the leading Marja’ because of great piety and the extent of knowledge he had acquired among the other Ulema and Maraje.