Marketed by who though? Like the article says, there is no main company or companies behind this. Just lots of random products cheap from China being resold.
I wouldn't be surprised if some smart folks in China launched a covert social media campaign to sell this stuff. You don't need much (aside from money and some dedication) to create a fad these days, as long as it's something simple and doesn't require extensive concentration to grasp.
They have been popular with folks that owned 3D printer for a while. It could be something simple like a critical mass of 3D printers being reached. My wife was printing these for fun a few months before it all exploded.