There are certainly immigrants with non-western values and also immigrants who are criminals but why are you mixing these two demographics together? If anything the ones dealing drugs are likely to be the most westernized.
I suppose you brought up Muhammed on the basis that his venerated status in Islam enables us to significantly extrapolate Muslim culture from his own personal culture. I will therefore state that the evidence of Quran/Hadiths yield evidence of great brutality in the person of Muhammed, which therefore may inspire brutality and violence in any devout followers of his, or in the broader Islamic culture. This is certainly conducive "creating criminal gangs".
[0] https://wikiislam.net/wiki/List_of_Killings_Ordered_or_Suppo...
There are migrants from the same countries that integrated well. The problem is mostly with the "asylum seekers" who never wanted to integrate.
These two facts make those people feel "safe" to commit high crimes.
It is both in this article and many others, it's not like this is a secret.