Hm… I will try to explain what is happening with images.
When a game starts, you see a lot of new players comming, almost everyone is “weak” and the game gets a wave of noobs and just a few players are actually strong, result:
After some time and enffort, more people gets stronger, this moment the game is relatively balanced and equal:
And then, the end. Many players are on a rush to get in top, and the the stronger, this results in a game with a large community of top players, with the best items and resouces, players that are in the top and will do everything to keep their position, the more top players, the harder it becomes to get to the top, and people starts getting stuck, because even having the best stuff is not enought to be a top player, as you can see here: