Earlier quoted context omitted.
I can't find the exact article. For some reasons "everything" pre-brexit about immigration has been buried by Google. However the route of African migrants through Italy to the UK was well known before Brexit. https://www.euractiv.com/section/uk-europe/news/african-migr...
You are mixing two things: Yes, illegal immigrants get into Italy from the Mediterranean sea. From there they move to north Europe, but this is far from getting Italian citizen and have the freedom to move in EU. However is sometimes very easy for many south americans to get Italian citizenship thanks to our dumb citizen law that grant citizenship to anyone who could prove to have kind of remote Italian ancestor
The argument was made that UK cannot control its borders from non-EU immigrants because Italy at the time was giving them enough papars so they could travel legally to the UK.
To be honest I cannot recall for sure if they were getting instant italian citizenship or just some form of residency. However in the end they could even get british citizenship because they would live in the UK long enough(i believe it's 5 years) using the EU papers. There was benefits fraud as well.
Unfortunately I cannot find the articles anymore. It's almost like a conspiracy that everything regarding immigration before Brexit is no longer search-able(I know it's just Google's algo discarding old news). Immigration was the issue number 1 for the british people before Brexit. I beleive it's not over yet as european politicians are still ignoring people's concerns on immigration.