The strength of this Islamophobic trope is essentially a media problem, caused by a combination of cynical sensationalism and clickbait headlining, and the power of unsubstantiated online claims that are so difficult to completely debunk. The term “no-go zone” in relation to tight-knit Muslim communities living in European cities seems to have started in the UK in 2008, when Michael Nazir-Ali, a Church of England Bishop, argued in a Sunday Telegraph article that Islamic extremism has created “no-go” areas for non-Muslims in many parts of the country, despite providing no names or evidence. Many on the far-right then picked up on this trope, but increasingly others in the mainstream media and in politics used these claims during the populist shift in politics seen globally in the 2010s.
Unsubstantiated claims like this have only become more common over the last decade as the shift to online news sources has meant that for many media consumption is completely dominated by crackpot conspiracy theory media, and social networking has left many in "echo chambers" where false claims are only further reinforced. However its not just a fringe media issue, its also a framing issue within legacy media, where the term “no-go” zones are often used in the headline but the story discussed is actually another issue entirely  and no evidence is provided for the casual sensational claim made in the headline. Hardline nationalists and the far-right have strengthened in the transition to digital media and found that online networking aids their cause, unfortunately the changing media landscape has also seen mainstream outlets try to occupy a similar market, and myths like this are perpetuated in both fringe and mainstream media.