As Iranian ambassador in Russia Kazem Jalali stated, Iranian request for Russian assistence was transferred at midnight between Saturday and Sunday. Despite the fact that these are weekends in Russia, the request was almost immediately satisfied and soon three Russian firefighters (1 IL-76 and two Be-200) flew to Iran and arrived in Bender Abbas on the night of Monday.
As far as I understand, the main danger there was that the fire could spread to the main part of the port infrastructure, which could cause very big damage to the Iranian economy. Fortunately, this did not happen, but the authorities of Iran and Russia correctly acted on the basis of the probability of the worst development of events.