Saying I have a muslim friend, he's cool, is not a counterpoint for a literal request for statistics. That statistic you presented was of one, albeit outliar in nearly all areas country. We need better/more data.
The mastermind (if you can call him that) of the November attacks last year, Salah Abdeslam, was also a petty criminal and was radicalized only recently before the attacks were carried out. At least one of the gunmen also had prior convictions for petty crime.
3 out of 5 of the attackers in Brussels this year also had prior convictions for non-religious crime (I wouldn't consider robbing a bank to be petty).
It's the same mechanism that makes Bloods and Crips.