Nobles had overthrown most of the monarchs by

You have to specify in what country? If the answer is France, they were mad at Louis XIV because he gave them no taxation yet no representation in government. This was very common in an absolutist government like France at the time. The nobles wanted the say in government so they teamed up with the peasants (had taxation and no representation) who were also very mad and they went to war with the monarchy. The monarchy lost because of the amount of people the nobles and peasants had.