It was originally just a meme like the way gar is. It was never considered to be anything serious till around like maybe 2009 when I saw some posts in threads about the issue in a serious manner. Some people realized they genuinely had feelings for these fictional characters and ran with the term waifuism.
Concept isn't new, people in ancient times would fall in love with statues, or even characters from fictional plays but not the actors themselves.
I think most on here don't care for the fact it's associated with a meme, isn't something you'd just think about all the time. Already a bit of outcasts to far to care about what other people may think.