doubled holding rewards when hive was 1-3$ with hope that people will take some profits for themselves at best prices, that's like second half of 2021 and january. Other changes are effect of governance, players decide in game about rewards distribution for both rankings rewards and holding rewards, so it changes from time to time.
For SIM, it goes down overtime cause income tax(sim price relation), but also if you don't adjust your city to game changes, you earn less. Like updates on popularity decreased bonus population by a lot.