The reason for your stalled progress is quite simple, actually. When you cut calories, however small your deficit might be, your metabolism begins to down-regulate. In an effort to conserve its energy for survival, your body begins to manufacture less metabolism-friendly hormones like thyroid, testosterone, and leptin so that your body can reach homeostasis.
For a simple picture of how this happens, take a 500 calorie daily deficit. This is supposed to result in about a pound of weight loss per week. But that is not going to happen forever, or you would obviously wilt to nothing.
Along the way in the weight loss process your body begins to slow down its metabolism to conserve valuable energy (fat, glycogen). Eat at that original 500 calorie deficit long enough, and your weight loss will eventually level out and then stagnate.
Reverse dieting helps you restore your metabolism to a much higher level so that you have a better “base” to cut calories from. Starting your weight loss at 2500 calories is going to leave you a lot more room to cut calories as compared to if you started off at 1800 calories.
The former will result in slower, yet more sustained weight loss over time. The latter will likely result in fast weight loss, quickly followed by stagnation, frustration, and then a falling into the yo-yo dieting trap.