I am guessing that it makes sense that very high profile people will have a higher percentage of fake followers than an ordinary, small account would because many of these fake accounts are bots that are set up in order to get attention for whatever they're selling or promoting by interacting with high profile accounts.
Well, there are different bots for different purposes.
A bot operated to post advert messages might want to post them on high profile accounts.
A bot for a "500 followers for $5" company might be more likely to follow low-profile accounts, with some random activity/follows thrown in as camouflage.
A bot operated to amplify certain messages/opinions might follow accounts of middling visibility, and focus on likes rather than more visible activity.
