Sadly, it seems much mundane than that to me: since the bulk of those players I see, politely referred to as netdeckers, are like sheep, driven by herd instincts, the popularity is probably determined, at least in a ‘first-order approximation’, as a physicist would put it, by the popularity of whatever ‘authority’ (a ‘streamer’ or self-proclaimed ‘meta guru’) they are following, e.g.: deck_popularity = sum_{i} streamer(i)_popularity * deck_play_rate_by_streamer(i) , or something along these lines. These seems in contrast to how a ‘meta’ would evolve if everyone would adhere to a rational strategy — although it could converge if those authorities were rational enough.
Indeed, how is this possible if a win rate of a deck that everyone plays is exactly 50% a priori, as noted also above? 