Oddly, I believe it speaks more to a specific population than a specific fetish. It is not that there are more people who have a foot fetish; it is that the people who patronize 'onlyfans' (and other sites featuring similar content) have a foot fetish. So, it appears to be more prevalent when it really isn't.Feet fetish is the only fetish that is interesting to me despite it not doing anything for me. Due to how fucking common it is and that its bloody everywhere. Once you notice it there are connections between feet and women and sex everywhere. And its not just recent either. Thats what makes it actually interesting. It has cropped up all over the world in different cultures through history since ancient Greece and India til now.
I keep reading numbers here and there saying its like "20%" of men have sexual interest in womens feet. Which sounds ridiculous to me. Way too much. Its all so speculative though, no actual numbers exist and then people argue semantics regarding if its at a level that meets a criteria for fetish. All I know for sure though is that women that do onlyfans stuff often report feet stuff as one of the most common requests. Like after boobs and ass and adjacent stuff like underwear and toys etc.
Most men are pretty basic T&A creatures yet feet seems to lurk there just behind.
Whenever I see a VN with a foot scene I immediately wonder "WTF?!" When Mallory made the joke in this scene, I literally laughed out loud. One of my favorite Youtubers constantly remarks how she will not show her feet because of the number of comments and DMs she receives asking for it. And she can't stand feet! That being said, fetishes are peculiar in themselves. Like you, I am interested in why these occur.