Because there is no credible evidence against him.Thats why,not because he is Muslim.
In USA ,Police would have had fabricated evidence by now. Anytime one comes home in USA,one wonders if police had been there going through your stuff ,computer and has not poisoned your food.
Police goes around soliciting false evidence by offering bribes. You have to know the system. Its not a question of being Muslim. Its the people and the system you are dealing with.