High rated players are much more powerful than lower rated players, and are therefore able to capture significantly more Dark Energy from the pool after each Ranked battle win. The amount operates on a quadratic curve meaning that a player with double the rating of another player will earn 4X more DEC after each Ranked battle win.
The other major factor in how much Dark Energy can be captured after a win is the player's Energy Capture Rate (ECR). Capturing Dark Energy is difficult work and players tire after many battles making them unable to capture as much Dark Energy as when they are rested. As a result, after each Ranked battle both players' Energy Capture Rate will decrease by 1% and, as players rest, their Energy Capture Rate will slowly increase over time at the rate of approximately 25% per day.
If a player is at an Energy Capture Rate of 50%, that means they will only be able to capture half of the Dark Energy after a Ranked battle win as they would have if they were at an Energy Capture Rate of 100%.