The rise of pretenders was not related to war or famine as neither appeared consistently with the pretenders. If there tended to be any form of famine during a pretender's rise it was during their claim to power and not inspired by it. Catherine's illegitimate rise to power through the assassination of her husband, Peter III, did not inspire the pretenders since Elizabeth, who came to power in a similar fashion to Catherine, never had the same problem.
Elizabeth
Catherine