Tarek Masoud, writing in Foreign Policy:
Though there is some truth to this narrative, June 30 was less a revolution than a counter-revolution, carried out not by the photogenic young people who made Tahrir Square a household name two-and-a-half years ago, but by the orphans of the regime that those young people had overthrown. Morsy's sin was not that he sought to Islamize the state -- Hosni Mubarak had done a pretty good job of that himself, and the temporary constitution issued by the new interim government includes all of the shariah-talk that liberals supposedly found so objectionable. It wasn't even that it tried to exclude liberals like Hamdeen Sabahi and Mohamed ElBaradei from governing. According to Sabahi himself, Morsy offered him the vice presidency shortly after coming to power last year. And although ElBaradei has just been named vice president for international affairs, it's safe to assume that the number of protesters who took to the streets to put this widely (if unfairly) maligned man in government is vanishingly small.
No, the sin of the Muslim Brotherhood was not that it failed to work with liberals, but that it failed to work with the old regime. For the almost the entirety of its time in power, the Brotherhood has demonstrated a remorseless, unyielding obsession with rooting out Mubarak's National Democratic Party from Egypt's political life. This extent of the obsession was on full display in one of the last speeches of Morsy's presidency. Before a crowd made up of equal parts dignitaries and rowdy Muslim Brothers from the provinces, he railed against the remnants of the ancien regime -- commonly called the fulul -- and then took a few minutes to tell an unflattering story about a man named Kamal el-Shazly, who was Mubarak's parliamentary enforcer -- and who has been dead since 2010. This odd detour into what is now ancient history reveals the extent to which Morsy and his Brothers viewed as Egypt's primary problem as not the crumbling of its economy or the decay in public order, but the continued presence of Mubarak's allies and appointees in almost every corner of the state apparatus. "One year is enough," the president declared, suggesting that the gloves were soon to come off and a full-blown purge was in the offing. In the end, he was the one who was purged.
Another way to see it was that Morsi and the MB completely failed to understand the fragility of their situation, their need for allies (and thus concessions to those allies), and that neither the army nor the Americans were reliable partners to maintain them in power.