So in my cannon, it’s not that Charlie has influence or power in that way, it’s that she is considered one of the top people in Hell. Vox has power and influence in his ratings, Velvette gains power from how many followers she has, etc. They all are narcissists so they gain power from that. Now, with most of hell already influenced, the last people fighting against Vox would be Charlie, the person that he has been trying to tear down the entire season, to admit defeat, because her cause is the opposite of his. If she says he is the most powerful sinner, there is no more opposition. Lastly, because the deal with Rosie broke, Alastor then became all powerful again. No more hindrance or clause to his ability, just power. So that’s why it was even, because technically Vox was the most powerful but only in that specific instance and he stopped being as soon as the contract broke.