When we’re discussing leverage, the two main components that we’re looking at are the mass of the different parts of the body and their various lengths. Unless you’re still growing, you can’t really change the length of your levers too much! This is the reason for the focus on increasing girth.
There’s generally a natural increase in strength and performance as you get heavier. Your absolute strength goes up. However, for most of us, we hit a point where we start to lose increases in absolute strength at the expense of relative strength. So while your total squat may go up, your squat in relation to your body weight may actually go down.
In the individual lifts, the squat and bench press are affected the most by increases in body mass. Whether it’s a bigger belly to bounce off of or shortening your stroke in the bench, increases in body mass tend to improve your squat and bench press much more than your deadlift.