Bottom line:
They knew he was going to do something but chose to do nothing because acting to stop him would have been “Islamaphobic” in their view.
or he could have been managed to create a False Flag.
Yes, but the service may also just be a little incompetent. Today I was reading that they were puzzled as to why the London Bridge attackers were carrying plastic 12” knives. Anyone knows that plastic can go undetected through most scanners, so the answer to the “puzzling” question is that they ordered the biggest plastic knife they could - probably in bulk, since they seemed to have about 10-12 knives of the same color (mauve) in the van and on their persons - because it would be hard to detect.