What does funding revolutionists supposed to do?

funded two of them (all I could afford), and all they did was sit on london chasing away the other lords...never attacked london or anything...a bunch of other revolutionists showed up around london too and sat with the others.

Is it pretty much a waste of money? I thought they'd actually attack and start a new country or something...instead they were rather useless.

I'm guessing they will chase away lords so you can siege in peace, plus chase and kill caravans so the city will become poorer which usually means the lord that owns it gets a slightly smaller party (lord party size used to be slightly tied up with the prosperity of his holdings, don't actually know if that's the case in this mod, but it was one of the reasons raiding villages was sometimes a good idea)