Could be any reason really - launch of new server thus more players, some massive overhaul update, also possible server migration or something signaling downtime, thus trying to appease and prepare the player base for it. Some more colab events with other games, some new game mechanic update... really it could be anything, and nothing at the same time. For all we know it just might be the usual summer promotions akin to Steam Summer sale, to throw bunch of stuff at people to show appreciation and such.
Who knows