Angles lead to strangles. The goal of jiu jitsu is a smaller person can defend themselves against a larger person. This is harder to do with a head-on attack. Nowhere in the universe does a smaller mass overcome a larger mass. You need to create an angle of attack to create leverage. A great example would be in takedowns. If a 100-pound woman and a 200-pound man push each other, the larger person would win, but if the woman changes her level by squatting, the man would tumble over her, giving her an easy takedown. Sweeps are basically takedowns while on the ground. The goal is to take the person off their base. Getting under a person’s hips makes this easier. Angles make joint locks easier if put on with proper leverage. Think of a crowbar or car jack. You always grab the handle at the end of the lever, giving you maximum leverage.