The West focuses more on its closer cultural ties, so yes, Brussels matters more to Americans and Europeans than Pakistan.
The time lag between the two locations, too, matters, though not as much. But the holiday weekend did slow down reporting of the holiday massacre.
A separate issue is the liberal media's desire NOT to report Islamic violence any more than they have to. Muslims targeting Pakistani Christians at Easter is completely in line with the Koran's hatred of Christians and the very belief Jesus was resurrected.
Nor does the event fit the narrative of Muslims as the underdogs who need sympathy along with reflexive hatred of Western society many liberals have. And you can't turn the Pakistani Christian slaughter into "the West was evil bombing Syria, so the bombing of X in US or EU is a response". Muslims killing Christians for being Christians is under reported whether it happens in Pakistan, Egypt, or Nigeria.
So they aren't reporting it in part because it seems to far away and removed from society, and partially because it doesn't fit the liberal secular narrative.