Why was Caliph Suleyman disliked by the noted generals in the Umayyad army?

Question

Caliph Suleyman of Umayyad Empire was by all accounts a rash man who kept a grudge. He also appears to have had stormy relations with the Army's Walidist generals.

His only apparent support in the Army was Yazid bin Muhallab, who was in Suleyman's debt from the days when the latter's elder Brother al-Walid was reigning (Yazid was imprisoned and tortured by Hejaj bin Yusuf and was safe only after Suleyman interceded on his behalf, making the Caliph order Hijaj to cease his attempts at murdering Yazid).

But on the other hand we see other senior generals of the Army like:

1. Hijaj bin Yusuf, opposed Suleyman's appointment as heir apparent and advocated succession of al-Walid's sons instead. One of the most loyal servants the Umayyad dynasty ever had, it's curious that he most vehemently opposed Suleyman Umayyad and was so frightened by the prospect of his ascension that he wished not to outlive Caliph Walid.
2. Muhammad bin Qasim, followed his uncle Hijaj and refused to accept Suleyman as the rightful Caliph.
3. Qutayba ibn Muslim, opposed Suleyman's appointment as heir apparent and advocated rights of al-Walid's sons instead.
4. Musa bin Nusayr, views on Suleyman's appointment unknown but held him in little regard as evident by the fact that even though Suleyman ordered him to hold off the triumph parade to celebrate conquest of Spain for a few days so that ailing Caliph Walid could die and Suleyman's reign would begin with victory parades and news of victory in the West, Musa refused to do so and held the parade and presented the plunder to the dying Caliph.
5. Tariq bin Ziyad, same case as Musa bin Nusayr.

Suleyman, for all his flaws, proved to be a capable ruler. Walid's sons on the other hand, Yazid III and Ibrahim, proved to be very ineffectual in their short reigns (But of course we have the benefit of hindsight which the Walidist Generals did not enjoy - Still it's unlikely that a shrewd Politician like Hijaj messed up in getting the right measure of the Princelings). Suleyman never forgot those men and all of them lost their stations and many their lives for opposing his succession and other offences.

What was it about Suleyman that the most generals disliked? Why is that the most loyal of the Umayyad dynasty's officers felt more loyalty to al-Walid and his sons than to Suleyman?

It is very likely that his short temper may have been part of the reason but I find it very bizarre for the bureaucracy to be against a ruler just because he was bad tempered. A lot of Kings and Emperors used to be very rash and prickly. It wouldn't be the first time either in history of Caliphs. When Caliph Abu Bakir appointed Umer as his successor, a lot of Generals and Officials voiced their concerns that he was short-tempered and strict. Abu Bakr's only reply was that burden of ruling would soften him up. Umar never faced opposition from the army like that. (But of course Umer was one of the leading Companions of the Prophet and therefore commanded respect of most of the people, Suleyman wasn't and didn't.)

Answer 1

Other than Suleyman's notorious short temper and tendency to keep grudges against people who caused offence whether real or imaginary, With further reading, it looks like that It wasn't Suleyman that the Generals personally disliked, rather his alliances.

For context, Umayyads themselves were Adnanite Arabs (Qaysids) but Princes and Caliphs often allied themselves to Qahtanite Arabs (Yamani) for political benefits. The historical rivalry between the two factions was described as harmless before Muawiya I of Umayyad Caliphate but it became violent when Marwanid branch of the Umayyad dynasty rose with the support of the Yamani faction and Hashimid claimaint Abdallah Bin Zubayr clashed with them, supported by the Qaysid faction. Umayyads triumphed and the new Caliphs strived to keep a balance between their erstwhile supporters (Yamanis) and newly reconciled subjects (Qaysids). Both factions however carried on sporadic raids on each other to settle their accounts as late as Caliph Abd al-Malik's reign who settled their complaints either by paying blood-money or by issuing warnings to the aggressor party. His reign is when the Qaysid's became allied to Abd al-Malik's brother Muhammad ibn Marwan whereas Yamanis allied themselves to his son, Suleyman who was at that time governor of Palestine. Yamanis also courted other Umayyads like Umar bin Abd al-Aziz who eventually succeeded Suleyman as Caliph.

Now fast forward to the timeline in question, Caliph al-Walid's mother was a Qaysid Arab noblewoman from Banu Abs clan which is why Qaysid generals like Qutayba (Belonging to Qaysid Bahila Clan), Hejaj and Muhammad bin Qasim (Both belonged to Qaysid tribe of Banu Thaqif) supported him. Musa Bin Nusayr's tribe is contested, some claim he was a Lakhmid (Yamani), others claim he was a son of Banu Bakr confederation (Qaysid). If he was a part of Banu Bakr, it would make sense that why would he be more loyal to al-Walid and his sons rather than Sulayman who, despite his Qaysid mother's heritage, had allied himself to the Yamani during his term as Governor of Palestine. Tariq's situation is also disputed. Some say he was a part of Yamani Kindah tribe, other say he was not an Arab at all but rather a Berber. In any case, Musa and Tariq do not seem to be as outspoken in their opposition like Hijaj and Qutayba, nor did they rise in rebellion afterwards like Qutayba. Their only offence appears to be subtle act of defiance shown to Suleyman in last hours of al-Walid.

Yazid ibn Muhallab on the other hand was part of the Azd tribe which was a part of the Yamani faction, so he naturally supported Suleyman as opposed to the claimants favoured by the Qaysids. Suleyman was their guy whereas his nephews were the enemies. Suleyman knew that he was very unpopular among the Qaysids which is why he did not move to Damascus even after becoming Caliph and remained in Palestine where his Yamani support base was strong. The reason why the Army seems to be stacked against Suleyman is because it was dominated by Qaysid faction under the reign of Caliph al-Walid. Caliph Suleyman's purge however changed the situation in favour of Yamanis.