I actually don't think it's a "degenerating into it" situation, but is instead a kind of self-grooming with pornography. I don't think you're going to find any cases of men who are consuming normal pornography, stop consuming that porn and switch to drawn or animated fictional characters. We certainly don't see older men switching into furry porn from regular porn. And furries are very clearly younger and male.

What I argue is that you have emotionally under-developed young men that find anthrophomorphic (literally human-like) characters to be very relatable. These anthrophomorphic characters are literally designed to be simple and easy-to-understand symbols of specific behaviors, attitudes, mental states, or emotions. As such, they tend to be extremely relatable because they are literary devices that act as a stand-in for the viewer's own internal dialogues. If these characters exude any kind of sexuality or romance, this can basically "cross wires" in an emotionally under-developed young man who can suddenly find that relatable character to be the closest thing they have to a "crush". Obviously most movies and TV shows don't go too far due to broadcast restrictions, but if these young men have access to internet porn, suddenly they'll literally have porn of those characters; which if viewed repeatedly will effectively groom their sexuality towards those characters rather than real women.

This is a long-winded way of saying, Krystal from Star Fox didn't make anyone a furry; it's that young men basically used Krystal as an outlet for sexual frustration that caused them to groom themselves into furries with internet porn.

This likely isn't any different from the rise of hentai use among young American men. I think all of the mechanisms are the same, the target of attraction is just slightly different