Where in the world would Ser Marston Waters get the idea to besiege his own Monarch, knowing that he is ultimately screwed when he lets them go. Or screwed if any of Aegon’s supporters, family members, and allies demanded he be released. This is his KING for goodness sake! The ruler of Westeros! He pretty much would have thought he signed his own death warrant doing that. Is there anything similar like that that happened in real life history?

This is something I really want from Fire and Blood Volume I, because you get the impression that politics were sliding rapidly into chaos – Hands of the King being tortured, Queens assassinated, everyone in charge dying, whatever the Lyseni Spring was – but we don’t have the details to explain how A led to B which gave us C. 

But yes, it’s happened. The trick is being willing to kill the king and replace him, or keep the king a prisoner, afterward.