People holding virtual cosmetic items that nominally had some value as collectables doesn't mean the whole thing was actually worth that much to society. If everybody tried to cash out their collection they would have soon found there was nothing close to 3 billion in value. The prices of these things were inflated by gamblers using them for speculation. And generally speaking, anything that teaches gamblers a lesson is good for society in the long run.

As for it collapsing Steam; not a chance. They didn't take away anybody's games, and that's what Steam is for to the overwhelmingly majority of users. The gambling addicts are a small minority and generally an annoyance to everybody else.