He took the throne after defeating his opponent, Sultan Abdul Hakkul Mubin during the Brunei Civil War.
Notably, he also attempted to return the throne back to the origin bloodline via Sultan Muhammad Ali's family.
Sultan Abdul Hakkul Mubin relocated the administrative center from Kota Batu to Pulau Cermin, in contrast to Muhyiddin.
[3][2] With the goal that Abdul Hakkul Mubin would remain put to weather the crisis that occurred prior to the Brunei Civil War, the relocation was carried out under the direction of the recently appointed Pengiran Bendahara Muhyiddin.
[2] Muhyiddin established his reign in Kampong Ayer after moving to the island and declared himself the 15th Sultan of Brunei, starting the country's first civil war.
[6] The Brunei History Centre of the Ministry of Culture, Youth and Sports hosted a session with an emphasis on the study of ancient Borneo manuscripts.
Sultan Muhyiddin's origin successor, Pengiran Muda Bongsu, who had fled to Sambas amid the outbreak of the civil war, was asked to return to Brunei and granted the title of Raja Bendahara.
Muhyiddin, who had lived in Kelaka, was requested to take over as ruler of the Sultanate of Brunei after Pengiran Anak Muhammad Alam's death, at last attained the throne.