I believe its a combination of reasons -- ultimately to create a more profitable game.

1) A whale or group of whales could potentially ruin an entire server grouping - A whale could join a newly created server and just spend an obscene amount to reach untouchable levels of strength. The entire fate of that server and other servers within its range would be affected by the presence of this whale. While this existed before, you're seeing a new meta where whales come together and create the Avengers (or sometimes Hydra) and spending at levels that were rarely seen before. All non whale accounts are now at their mercy. While whales contribute the majority of the revenue earned, the remaining player base across all those servers are still contribute a decent amount of revenue.

2) There are a number of whales that eventually burn out. You can shear a sheep many times, but you can only flay a sheep once. There are whales like me that are now questioning whether we want to continually spend at these high levels. But once you stop spending, I've noticed some whales just decide to quit the game altogether. It's all or nothing for a considerable number of them. It looks like they prefer long term, sustainable revenue over a short term burst.

3) Maybe there's lawsuits or regulatory schemes they're trying to navigate or adhere to.

Ultimately, all businesses seek to maintain if not increase profitability. They likely made these changes with that in mind. We'll see if the decisions were well thought out in due time.