During Abu Sa'id's lifetime, Hasan Buzurg was also called upon by Ghiyas al-Din to help stop rampant tax abuses in eastern Iran.
[5] However, Arpa's rule was not accepted by a part of Oirats, whose leader and the governor of Baghdad - Ali Padshah was an uncle of Abu Sa'id and had his own designs on throne.
Claiming Abu Sa'id's wife Dilshad Khatun was still pregnant, he raised Musa, the grandson of Baydu as rightful heir to the throne.
[8] After defeat of Arpa by Ali Padshah on 29 April 1336 and subsequent murder on 15 May 1336, Hasan Buzurg saw his chance and raised a child, Pir Husayn from Tabriz, a great-grandson of Möngke Temür, to claim the position in alliance with Hajji Taghay, the Sutaid claimant to Diyar Bakr in opposition to Ali Padshah.
Pir Husayn was crowned in Anatolia on 20 July 1336 with the title "Muhammad Khan" and Hasan left for Iran, leaving his deputy Eretna behind to act as governor.
[5] Shortly afterwards, however, several descendants of Chupan united under his grandson Hassan Kuchak, who used a slave called Qara Juri to impersonate his father Timurtash in order to legitimatize his cause.
[12] Shortly after defeat by the Chobanids, Qara Juri was dismissed by Hassan Kuchak and was later routed by Hasan Buzurg.
Following his abandonment of Togha Temur, Hasan Buzurg recognized Jahan Temür, a grandson of Gaykhatu, as Ilkhan near Hamadan.
[13] The conflict with the Chobanids again boiled over, and Hasan Buzurg and Jahan Temur met Hassan Kuchak and his new puppet Suleiman Khan in battle on the Jaghatu.
In return, al-Malik was promised that his son-in-law Ibrahim Shah Sutayid would be granted Diyar Bakr instead of pro-Jalayirid Hajji Taghay.
After he stopped recognizing Togha in 1344, he still did not proclaim himself independent, and ruled with the title of ulus beg, as a mere governor, simply leaving the Ilkhan throne unfilled.
The murder of Hassan Kuchak in 1343 did not provide much relief, for his brother Malek Ashraf sent an army to conquer Baghdad in 1347.
Hasan Buzurg continued to play an influential part in Persian politics; he assisted the Injuid Abu Ishaq against the Muzaffarids, helping him restore his rule in Isfahan in 1353.
Furthermore, he attempted to unify Persia; he had sent a Muhammad-I Mulai to act as governor of Khurasan, for example; the latter was later executed by Togha Temür's military commander Arghun Shah.
In attempting to maintain the Ilkhanate, he ultimately failed, and in some ways accelerated its disintegration, by preventing other forces such as the Chobanids from gaining more influence.