I think it sits somewhere in between scapegoating (assigning the blame to another person or less often some other force) and "everything happens for a reason". It's a basic psychological need to find causality, especially for upsetting things in life. There is in fact no shortage of attribution theories in psychology, and covariation (same causes leading to same effects) sits fairly highly among them. So if one heard that X commited suicide because of the Blue Whale, and then Y commits suicide and someone else mentions Blue Whale... However, in this case it's probably more appropriate to quote another media article on the Blue Whale moral panic:
French anthropologist René Girard famously studied how moral panics ultimately derive in scapegoating. Whenever a society goes through difficult times, there is the tendency to unfairly blame an individual or a particular group for all the troubles. The collective animosity builds against these scapegoats, and very frequently, they are either killed or exiled, as an attempt to put an end to the crisis. This is the psychological mechanism at work in lynchings and purges.
[...] The Blue Whale designers, whoever they may be, are scapegoats.
The Blue Whale moral panic is far from being the first in its kind. The idea that some media product (a song, a movie or a videogame) has the power to drive mindless kids to kill themselves is quite ancient. The first version of this cultural trope goes back all the way to the 14th Century, with the famous Piper of Hamelin story. According to this legend, a piper was hired to rid a town of its rats; the piper played a melody that drove the rats away; the townspeople refused to pay, and as revenge, the piper played a melody that made the kids mindlessly walk into a river, thus being drowned. The Piper of Hamelin story is clearly fantasy, well suited for the credulous medieval mentality. The Blue Whale story seems to be along the same lines, and unfortunately, the same credulous and paranoid mentality is at work.
Listening to a song or playing an internet game will not make anybody commit suicide, unless that person already had previously strong suicidal ideation. In that case, alleged instigators such as Blue Whale or Judas Priest would be scapegoats.