the thing here as I've seen in many other p2w games is that players has joined a new server, paid for the first bonuses to get a big head-start, played for a few weeks, been caught up to by bigger spenders. At this time they feel its time to move on and try again on a new server. This keeps going until they hit the jackpot where there are few players that spend money, meaning this "server jumper" now is the strongest.

At least how I've seen it, could be wrong.