Yes and no.
I remember very well the period when Mubarak was under siege.
The Brotherhood was very much in evidence and many of us were very concerned that they would end up in control.
So yes, they may not be the majority, but they had the rabble rousing skills to pull it off.
Had Mubarak killed more of them, Egypt might be better off today but of course we will never know. We can only speculate.
That said, if the army manages to kill them all it will be a blessing to the world.