Why did investigators focus on Molenbeek-Saint-Jean after the Paris attacks?

Investigators focused on the Brussels commune of Molenbeek-Saint-Jean following the 2015 Paris attacks because it was identified as a potential hotbed of militant Islamist extremism and had produced a disproportionate number of foreign fighters for the Syrian Civil War.12

The area was directly linked to the plot through several key figures:
* Abdelhamid Abaaoud: The suspected mastermind of the attacks was a Molenbeek native who had grown up in the commune and maintained extensive ties there, including connections to several of the Paris attackers.1
* Salah Abdeslam: Another Molenbeek native, Abdeslam was a primary suspect sought by police for his role in renting vehicles used by the attackers and serving as a driver. He was eventually captured in Molenbeek after four months on the run.12

Counterterrorism experts noted that the fragmented administrative structure of the Brussels-Capital Region, which included multiple police departments and political bottlenecks, contributed to an environment where vulnerable residents could be exploited by extremist recruiters.2