Why're this game so much ore popular than all the other King of the hill type games
It is the only one that hasn't repeatedly let its audience down, yet.
The Culling had a disastrous patch and even before that was mostly melee weapons which isn't as appealing to the shooter fans.
H1Z1 KOTK has had a number of outstanding problems that go unaddressed one patch after another to the point where long time players feel they're never going to get fixed. On top of that the influx of high ping cheaters from other regions is a plague according to some. Game seems to still be growing in Asia if not so much in Europe/NA. Still putting up similar numbers to PUBG, but doing so on what, four times or more the player base?
Looking at Steamcharts it looksl ike PUBG is easily going to surpass KOTK unless Daybreak pulls a rabbit out of their hat in the very near future.
KOTK: 134k peak, 5 million owners(not sure if this includes original and/or the other half of the split). PUBG: 124k peak, 1.3 million copies. Of course it remains to be seen if PUBG will maintain its growth after the streamers inevitably move on to something else.