So, it’s this kind of topic? 
Alright, I’ll respond accordingly, although my projection is that not everyone’ll actually get it. One more disclaimer: I’ve not read through all of the replies thoroughly, sorry if I’ve missed something noteworthy.
Exactly because it’s rigged, according to the assumption made.
To begin with, let me play Captain Obvious and point out a couple of things that are… obvious… obviously.
First, in such a multiplayer game where one player wins and one player loses, there cannot generally be any ‘miracles’ and ‘wonder decks’ with e.g. 80% winrate — in fact, that number tends towards 50% (if there is that one deck that is much stronger than any other, then essentially everyone’s gonna play it, the winrate becoming strictly equal to 0.5) for any competitive deck. It’s not even chess either, so brilliant risk-calculating and decision-making can make a difference between 49% and 51%, for instance (provided the game is not rigged — that’s how top players in something like poker succeed), but nothing like a 100% winrate, to which we’ll get back later.
Second, if the game is rigged for someone to lose — then it’s simultateously rigged for someone to win, obviously. Is the question, then, why you getting the ‘boon’? We don’t know all the details of the rigging algorithm, but one can make reasonable assumptions. For example, I haven’t seen you post anything especially smart (haven’t looked very hard, but still), and I doubt you could possibly be, either — maybe you even play accordignly, thus the algorithm alotted you enough ‘privilege points’ [1] for getting such… paraintellectual help from it. ‘Well done, Sunshine…!’
There’s still room for ‘improvement’, though: notice this brilliant guy at rank 1 Legend [2] — 100% winrate, as mentioned above. Way to go!
One more thing: apart from ‘ekwality’ [1], there’s another kind of ‘rigging’ and ‘rng’ for so-called streamers (and ‘top’ players who get invited to all those tournaments, comment them and so on) — not all of them, but a special kind appointed to promote the game. Haven’t taken a look at them for years, but from the old days, you probably remember the type: those guys with big glasses (apparently, supposed to make them look cool and skilled 
) in their twenties with alleged 30+ years of ‘professional’ experience at other best-selling card games (apparently, it is supposed to sound cool), bonus points for unusually-coloured hair and dancing on their Gaming_Chair™ frantically in order to make their Ragnaros shoot just the one right target out of eight fifty times in a row as a display of true skill. What I’m saying is that these guys are poster children of the game promoting its image — even if you turn on your Twitch channel and show your 120-IQ decision-making, don’t expect the same kind of success. 
So, yeah, to sum up, those top ranks often appear to be filled with either these ‘big streamers’ or ‘40-ICQ’ nice guys with ‘genius’ battletags like ‘iNevuhBathe’ or ‘PloughUrMamaInDaLips’ and a brilliant playstyle, as illustrated above [2], as a result. One more thing: I remember climbing from ‘Rank 25’ (or is it Bronze 10 now?) all the way to Legend (in Classic) after a long hiatus (i.e. no bonus stars), and I haven’t seen ‘newbies’ with basic decks etc you’d expect — it’s mostly the same kind of netdeckers with the same level of play… oh, and bots, too, highly likely, which are a separate issue (there are dedicated topics about that) and can be farmed with an ‘impossible’ (under normal circumstances, that is) winrate.
References:
[1] https://www.youtube.com/watch?v=iKcWu0tsiZM
[2] https://www.youtube.com/watch?v=-jenlSf2E8o