A study for the United Nations Office of Counter-Terrorism found that despite claiming to protect Muslims, most of the returned foreign terrorist fighters [FTFs] were "novices" in their religion and some did not know how to pray properly.
"Most saw their religion in terms of justice and injustice rather than in terms of piety and spirituality," said the authors of the report, which was based on interviews with 43 people from 12 countries.
They found that a typical fighter "is most likely to be male, young and disadvantaged economically, educationally, and in terms of the labor market".
"He is also more likely than not to come from a marginalized background, both socially and politically," the reported added.
"Most were unemployed, or underemployed, and/or said that their life lacked meaning."
Three quarters of those interviewed reached Syria but subsequently decided to leave, while others were intercepted by authorities in their own country or stopped en route.
Despite an appeal to all UN member states, the authors expressed regret that only seven countries agreed to participate in the study - three from the EU and four from the Middle East and North Africa.
Professor Hamed el-Said, of Manchester Metropolitan University, and terrorism expert Richard Barrett met most of the returnees in prison or under the watchful eye of security services.
The majority of interviewed fighters, who attempted to join groups including the Wahhabi Daesh [Arabic acronym for "ISIS" / "ISIL"], al-Qaeda affiliate al-Nusra Front and Ahrar al-Sham, came from large and dysfunctional families in deprived parts of cities where they were "isolated from mainstream social, economic and political activity".
"Religious belief seems to have played a minimal role in the motivation of this sample," the report found, saying economic factors had become more important as terrorist groups promised wages, homes and even wives.
The findings supported previous research using leaked Daesh documents, which showed that most recruits profess to have only a "basic" knowledge of reilgion, and warnings of a growing "crime-terror nexus" seeing violent criminals travel to Syria in the hope of "redemption".
Following the declaration of Daesh in 2014, the group produced a huge amount of propaganda seeking to attract Muslims with the promise of life free of supposed Western oppression, lived in comfort and peace.
Rose-tinted videos sought to present a utopian existence, showing smiling militants engaging in activities like bee-keeping, farming and even pizza-making as Western fighters used Twitter to broadcast images of palatial homes, swimming pools and expensive cars provided by the "caliphate".
The UN report said the propaganda exerted a powerful pull on young men who feel they have little prospects at home, especially when combined with perceived grievances and a wish to protect Muslims in areas of Syria.
"For some, this sense of brotherhood was reinforced by a sense of religious obligation," it said.
"The respondents of this survey claimed they did not go to Syria with the intention of becoming a terrorist, nor did they return with that purpose in mind."
Despite the role of propaganda sparking a global crackdown on extremist online activity, the report found that among surveyed fighters, the internet played "a far less significant role as an independent source of radicalization than is generally assumed, and certainly a far less significant role than real life contact".
The authors found that would-be "jihadis" went online to confirm and strengthen ideas that were already taking root, adding: "The internet then played a key role in reinforcing a decision that had in part been taken already."
Far more important was friendship circles and social networks formed around mosques, prisons, schools, universities, neighborhoods or the workplace - a conclusion supported by the high number of known British militants who were part of radical networks or left the country with friends and relatives.
The UN report said identity politics played a key role in radicalization, warning of "significant policy implications" arising from perceived injustice and discrimination.
It added: "Bad governance, especially disregard for the rule of law, discriminatory social policies, political exclusion of certain communities...harassment by the security authorities, and confiscation of passports or other identity documents, all contribute to feelings of despair, resentment, and animosity towards the government and provide fertile ground for the terrorist recruiter."
Although their accounts are highly unreliable, several imprisoned former Daesh members have blamed the security services for their radicalization.