My Kcal maintainence is 4000kcals. If I want to drop weight, I usually do so by dropping 500kcals off this so my new intake in 3500. Now consider, what if I instead opted to increase cardio to burn off 500kcals instead of altering my diet meaning that my diet remains at 4000kcals but now my maintainence has increased to 4500kcals due to added energy expenditure. Either way, i'm still at a 500kcal deficit and I will lose the same amount of mass p/w but I have approached this at two different angles.
Many people attribute cardio to increased weight loss but that is because they drop both calories and increase energy expenditure. As an example, At 4000kcals someone might drop their calories to 3500 to start losing mass but at the same time increase calorie expenditure by a further 500kcals meaning that they are actually at a 1,000kcal deficit. You can acheive the same results by lowering either kcals to the same amount.
Say if I decided to take on your program and my maintaince was again 4000kcals and I ate at 4000kals, regardless of how much cardio I do, i'm never going to lose body mass.
Training programs are undoubtably important,no question. But never underestimate the importance of a diet or a well-balanced training program.