Egypt has negligible amounts of oil. It needs tourism, and it needs Western companies being comfortable about coming in and doing business, neither of which is going to happen under Morsi.
The common people know they have to get rid of Morsi or they will starve. If it means killing off the Islamists, then so much the better.
It would be a major hoot if the disaffected Muslims all converted to Coptic Christianity and started refusing to speak Arabic. Unlikely. Too much stupid juice in the drinking water. But I can dream.