Egypt has always had a tremendous amount of poverty-- much worse than many Americans know. But under Morsi-- it got considerably worse still!
So my guess would be that at least part of those huge anti-Morsi crowd sare made up of people who actually voted for him (many who even would prefer an Islamist gov't to a democracy)-- but who are getting desperate because they are literally finding it becoming impossible to feed their families.
(I could be wrong, but from what I know about Egypt, there are more people who would prefer an Islamist government than there are who want democracy-- but many of these are angry at Morsi because they can't even afford to buy bread).
the Muslim Brotherhood is really the only party today that can be elected. That's the problem. The parties are so fragmented that there really isn't any path to power for them, and the brotherhood not only has the political apparatus, it also has the social one (its charities) that creates the mind presence that is needed to win an election.
So one can have another election today, and the Muslim brotherhood would more than likely win.
I think the writing was on the wall when Morsi was "elected". It was fairly obvious he had extremist interests and his interest in leading had more to do with power then leading (not one and the same in my opinion). I'm not surprised we are seeing increased unrest in Egypt. I think that the superpowers sometimes support less then ideal leaders because perhaps they feel it's better then the unknown? Makes me think of Pakistan and Afghanistan. Corrupt leaders, but one has to wonder what is waiting in the wings. When I see a superpower supports any particular leader, I think there has to be way more going on behind the scenes then we are privy to.