Umar was responsible for getting the bitterest enemies of Islam(Bani Umayyah) into Power

Umar appointed Usman through a consultative committee( as-shura ).

Let us see what Usman did after becoming the Caliph.

As sooon as `Uthman's came  to power Banu Umayyah got ground and began plundering the Bayt al-mal (public fund), and just as cattle on seeing green grass after drought trample it away, they recklessly fell upon Allah's money and devoured it. At last this self-indulgence and nepotism brought him to the stage when people besieged his house, put him to sword and made him vomit all that he had swallowed.

The maladministration that took place in this period was such that no Muslim can remain unmoved to see that Companions of high position were lying uncared for, they were stricken with poverty and surrounded by pennilessness while control over Bayt al-mal (public fund) was that of Banu Umayyah, government positions were occupied by their young and inexperienced persons, special Muslim properties were owned by them, meadows provided grazing but to their cattle, houses were built but by them, and orchards were but for them. If any compassionate person spoke about these excesses his ribs were broken, and if someone agitated this capitalism he was externed from the city. The uses to which zakat and charities which were meant for the poor and the wretched and the public fund which was the common property of the Muslims were put may be observed from the following few illustrations

1. al-Hakam ibn Abi'l-`As who had been exiled from Medina by the Prophet was allowed back in the city not only against the Prophet's sunnah but also against the conduct of the first two Caliphs and he was paid three hundred thousand Dirhams from the public fund.

(Ansab al-ashraf, vol.5, pp.27, 28, 125)

2. al-Walid ibn `Uqbah who has been named hypocrite in the Qur'an was paid one hundred thousand Dirhams from the Muslim's public fund. 

(al-`Iqd al-farid, vol.3, p.94)

3. The Caliph married his own daughter Umm Aban to Marwan ibn al-Hakam and paid him one hundred thousand Dirhams from the public fund.

(Sharh of Ibn Abi'l-Hadid, vol.1, pp.198-199).

4. He married his daughter `A'ishah to Harith ibn al-Hakam and granted him one hundred thousand Dirhams from the public fund. 

(ibid.)

5. `Abdullah ibn Khalid was paid four hundred thousand Dirhams. 

(al-Ma`arif of Ibn Qutaybah, p.84)

6. Allowed the khums (one fifth religious duty) from Africa (amounting to five hundred thousand Dinars) to Marwan ibn al-Hakam. 

(ibid)

7. Fadak which was withheld from the angelic daughter of the Prophet on the ground of being general charity was given as a royal favour to Marwan ibn al-Hakam. 

(ibid.)

8. Mahzur a place in the commercial area of Medina which had been declared a public trust by the Prophet was gifted to Harith ibn al-Hakam. 

(ibid.)

9. In the meadows around Medina no camel except those of Banu Umayyah were allowed to graze. 

(Sharh of Ibn Abi'l-Hadid, vol.l, p.l99)

10. After his death (`Uthman's) one hundred and fifty thousand Dinars (gold coins) and one million Dirhams (silver coins) were found in his house. There was no limit to tax free lands; and the total value of the landed estate he owned in Wadi al-Qura and Hunayn was one hundred thousand Dinars. There were countless camels and horses. 

(Muruj adh-dhahab, vol.l, p.435)

 11. The Caliph's relations ruled all the principal cities. Thus, at Kufah, al-Walid ibn `Uqbah was the governor but when in the state of intoxication of wine he led the morning prayer in four instead of two rak`ah and people agitated he was removed, but the Caliph put in his place a hypocrite like Sa`id ibn al-`As. In Egypt `Abdullah ibn Sa`d ibn Abi Sarh, in Syria Muawiyah ibn Abi Sufyan, and in Basrah, `Abdullah ibn `Amir were the governors appointed by him 

(ibid.)