1) Khan is from England and is of Pakistani descent. You say there are also Pakistani Americans, but the Filipino-American population is about 10 times the size of the Pakistani-American population. Plus, boxing is a bigger sport among Filipinos.
2) The opponents. Donaire was fighting a legendary Mexican warrior in Arce. Khan was fighting some Chicano nobody in Molina.
True. Donaire has drawn crap at the gate and on TV in the US in spite of the large Filipino population. Even when he fights in LA in high density Filipino areas he does not draw and can only get less than 2,000 to the gate. The only reason why the TV numbers for the Arce fight was huge is because of Arce and the only reason why that fight out-drew the Khan fight is because HBO has a much larger subscriber base than Showtime.
Timothy Bradley did not and had no right to claim he drew over a million PPV's. He knew the only reason he had those numbers were because of Pacquiao. Before Pacquiao he could not even draw 2,000 to a live gate and no one would give him his own PPV. Likewise with Donaire. Anyone who thinks he could headline a PPV is dreaming.
Arum and Top Rank used to Have Chavez Jnr in his own Top Rank inhouse PPV shows where he sold about 400,000 buys. Even at that rate at $50 a pop he was bringing in $20m. If Arum thought Donaire could do those numbers he would be putting him on an inhouse PPV as there is no way HBO or Showtime would do it.