Durovis Dive was out before Google Cardboard (consumer version of Dive released in November 2013, Google Cardboard was announced in June 2014). Furthermore, there were VR headsets before the Oculus Kickstarter, VR is not a new field, it's just never truly been mainstream before (though it looks likely that it'll breakthrough to the mainstream in 2016).
I think it's not a real "serious" product; more of a "gag", if anything.
I think it was Google's way at having fun with all the VR hype around last year's I/O conference (and to show it's not anything really groundbreaking).
A bunch of Chinese companies started pumping out Cardboard clones pretty much as soon as it was announced and at least one commercial VR porn company is using them.