On August 19th Eugen reset every ranked rating to 1500 and started Season 5.
AAR-Labs had no concept of a season, so the leaderboard kept showing Season 4's
standings: the top of the board was full of players who hadn't played a game
since the reset, while the actual Season 5 leaders sat far below them. Ranks,
rating brackets and the median were all measured against the same stale list.
That is fixed, and seasons are now handled properly from here on.