Wearing tails and animal themed clothing isn't particularly exclusive to members of the furry fandom
It's been a part of various human cultures.
I use to skate wearing a tail before I knew what I furry was.
The clothing company Animal aren't furry related, despite the name and I very much doubt Hugh Hefner chose the whole bunny theme for playboy because he is a furry... 'cus I am sure he is not.
People, especially girls, sometimes wear clothing with cute cartoon animals on them accompanied by amusing captions, again - it hasn't anything to do with the fandom.
Tons of cartoonists choose to draw animals specifically.
A lot of writers and graff artists incorperate animals into their work.
A ton of videogames and movies are themed around animal characters.
There are cultures and religions that revolve around animal worship and animal spirits etc.
The point I am getting at is, these things don't exist because of the furry fandom. The furry fandom exists because of these different aspects of mainstream culture and sub-cultures. The furry fandom may incorperate said aspects, and also build upon them. But 'furry fashion' doesn't really exist. The reason furries choose to wear tails and ears and whatever is often different to the reasons people outside the fandom may choose to indulge in such fashions. It's not furry fashion going mainstream, and probably has little or nothing to do with the fandom itself.
... I am sorry for getting so carried away
This whole mainstream furry-like fashion thing is probably related to that whole werewolf teen kids thing that made the news.