I'd like to add that it's overwhelmingly likely FD made this decision because of their often-stated concern that Powers expand too rapidly and lead to deadlock, especially because Powers cannot directly invade each other.
The clear answer to this problem is not to make the process of expanding, controlling and preparing so tedious and unrewarding to the player that most of them don't want to do it--that defeats the entire point of Powerplay.
They could solve the imbalance in an instant by keeping weekly credit reward levels the same, raising the number of merits earned per destroyed enemy ship to 20, and multiplying the trigger needed to cause an event (prepare, expand, or control) by 30.
What will happen instantly is a flood of undermining players will rush back into the core activites of Powerplay due to balanced rewards. However, this flood of new players--preppers, expanders, and controllers--will be offset by the increase in the trigger required to make each of these activities successful.
INSTANT balance, fair merit rewards, no change in expansion rates, and almost identical levels of time played for credits earned.