The Baronial Council and the Reformer Local Government

In 1258, the baronial council effectively deposes Henry in a way or at least takes power from. How does that happen? I mean, how can they just march in and say, right, we're in charge? So that's radically, radically new, revolutionary new. The other extraordinary thing about 1258 though is that of course this is combined with this huge reformer local government. Now, Magma Carta too had tried to reform local government and many of the clauses rained against the king's local government officials, the sheriffs. What's dramatically, extraordinarily new in 1258-59, and again, I think there's no parallel in English history to this,