you forget that the present government replaced the previous government and killed many of them. there are plenty of the displaced still lurking around and capable of planting the device as service crew at the resort.
the Brotherhood survivors might have become ISIS
No, I don't. I believe you are refering to the Obama, CIA US State department funded and supported Muslim Brotherhood "Arab Spring 'rebels'" that deposed Mubarek, and installed Muslim Brotherhood convicted criminal Morsi.
the (Muslim) Brotherhood survivors might have become ISIS
Or they might sitll be working for Obama and the US State Department, insisting the Egyptians restore Morsi to power, ...or else.