Al Jabarti- A scholar of Al-Azhar during the times of Muhammad Ali in Egypt- wrote on the Wahhabis when the Egyptian Army was sent to defeat the ikhwan movement (armed tribal forces of "wahhabi zeal" that fought the jihad to unite Arabia);
Some commanders, who were considered pious and devout told me, " How can we win when most of our soldiers belong to different confessions and some of them do not believe in anything and profess no religion? We are carrying boxes containing alcoholic drink, the azan [Muslim call to prayer] is never heard in our camp, the [Islamic] prescriptions are not fulfilled or even remembered, our people have no idea of religious rites. As for our enemies, as soon as the muezzin's call sounds, they perform ablutions and line up behind their single imam humbly and obediently. When the time for prayer comes during battle, they timidly perform the "fear prayer" [a shorter prayer] - one detachment goes forward and wages the battle while the others pray behind it. Our soldiers are astonished; they have never heard of it, not to mention seeing it. The Wahhabis shout from their camp, "Come and fight us, you pagans, you beard-shavers, who glorify libertinism and sodomy, you drunkards who have forgotten prayers, you usurers and murderers who permit yourself to forbidden deeds!"
The Wahhabis were demonized by all great powers at the time, they were anti-elite in their core and did not approve the way the Hijaz (Makka Madina and Jeddah) were rueled, certinly the purfication of the Holy Cities not only from polytheism but from major sins was a motive for their conquest. Hijaz was ruled by the Sharifs (/Ashraf) whom later were to collaborate with the British and for a while rule Syria and Iraq as well asJordan whom's royal family is still in authority.
"The strict morals introduced in Mecca ran counter to its people's customs and habits. The status of the holy city made its inhabitants feel superior to all other Muslims and led them to excuse a certian lewdness of behaviour. Whole blocks of Mecca belonged to prostitutes, who even paid a tax on their occupation. Homosexuality was widespread. Alcohol was sold almost at the gate of the kaaba and drunkness was not uncommon" 
what is Known as Saudi Arabia today was the result of King Abdul Aziz's conquest of the Hijaz, the Wahhabis in fact have conquered it before but were also expelled by Muhammad Ali's troops that committed horrible atrocities against tribes and villages that had their allegiance to the movement and resisted. Women and children were slain and their ears were sent to Istanbul ( I read this somewhere cant remember where but it was an academic book (the ears part)).
The first conquest was repelled by a modern and more advanced army; that of Muhammad Ali of Egypt, and went far into central Arabia in al-Dariya the capitol at the time which fell.
in Cairo october 1818 a festival was held in celebration of the fall of Dariya, fireworks and public merry-making took place. The Sultan (of the Ottoman Empire) professed his "profund satisfaction".
The Emir Abdullah of Dariya, his imam and the minister were taken prisoners, sent to Cairo and then to Istanbul. I was personally told by a historian professor, that Abdullah was hung by his feet till his death and that music was played to him! (they believe Music is Haram/forbidden)
But The russian embassy reported otherwise. that the three were brought infront of the Sultan, and his ministers and heads of the empire in heavy chains. surrounded by a crowd of idlers. The Sultan orderd they be executed. Abdullah beheaded infront of the main gate of St. Sophia, Imam at the entrance of the palace and the minister at the entrance of the market. Their bodies were displayed with their heads under their arms for three days then thrown into the sea.
All insolvent debtors were released from jail, the government took the expense of their debts at
"His Majesty's" expense and money was distributed to mosques and madrasas, to "thank heaven for its mercy" 
all from the book;
Vassiliev, Alexei (1997). The History of Saudi Arabia. Saqi Books: London.
page 138- from the travel notes of J.L. Burckhardt
 page 155