At the end of the English Civil War, the monarch was executed and replaced by "Oliver Cromwell", since at first there was a massive power vacuum that needed to be filled.
I can't really answer your question (as I don't really know enough about 18th century France), but I just want to clear up an (understandable) misconception about Feudalism in your question.
The French revolution was adamant and explicit in its abolition of 'feudalism'. However, the 'feudalism' it was talking about had nothing at all to do with medieval 'feudalism' (which, of course, never existed). What the revolutionaries had in mind, in my own understanding of it, was the legally privileged position of the aristocracy/2nd estate. This type of 'feudalism' was a creation of early modern lawyers and, as a result, is better seen as a product of the early-modern monarchical nation-state, than as a precursor to it. It has nothing to do with the pre-nation-state medieval period, or with the Crusades.
Eighteenth-century buffs, feel free to chip in if I've misrepresented anything, as this is mostly coming from my readings about the historiographical development of feudalism, not any revolutionary France expertise, so I may well have misinterpreted things.
