Because they feared Cersei, their fear my have been lost after her Walk of Atonement but after blowing up the Great Sept of Baelor it was most certainly back. This is part of the reason why the High Sparrow took power, he made it so the many stopped fearing the few and took control.
High Sparrow: Have you ever served the field, Lady Olenna? Have you ever reaped the grain? Has anyone in House Tyrell? A lifetime of wealth and power has left you blind in one eye. You are the few. We are the many. And when the many stop fearing the few...
Game of Thrones, Season 5 Episode 7, "The Gift"
On top of that the many had to be united to be able to properly overthrow the Crown, as again the High Sparrow comments. Once the Sept is destroyed and the Faith Militant destroyed with it the people have no one to lead them to unite together against the few and go back to fearing the few; especially under the circumstances that Cersei regained control.
Jaime: They should be closer if you mean for them to save you.
High Sparrow: I don’t. They’d never reach me before you struck.
Jaime: I’ve fought against worse odds.
High Sparrow: No doubt many of us would fall. But who are we, hmm? We have no names, no family. Every one of us is poor and powerless. And yet together, we can overthrow an empire.
Game of Thrones, Season 6 Episode 2, "Home"