I’m guessing that they did a background check and found something. They are even checking social media activity these days. They knew he was a muslim when he was allowed to board the plane.
I don’t have access to facebook or any other social media so I can’t check. I wonder if he has some history of jihadist tweets or facebook posts. Just going by two different names might be enough to deny entry in conjunction with a few violent posts. Especially when you choose to call yourself Mohamed but your birth name is something else.
Mohammed Abdal Miah jailed for urging others to join Isis
Two other guys with the same last name:
Another guy with the same last name:
It must be a very common last name.