After you've been lifting a while, you generally find you either want maximum strength or maximum looks.
When you're a weightlifter, increasing your strength is your sole objective. Powerlifters are an extreme version of this.
But why the lower number of sets and reps with high weight?
Heavy weights are well known for increasing strength, and you need more strength.
Why the 3-5 minute rest period?
This part has to do with muscle recovery and is a main difference between bodybuilding and weightlifting. The longer rest period has been shown across multiple studies to result in overall bigger strength gains. The rest also allows you to continue lifting, resulting in more gains.
More scientifically, it's the resynthesis of CP (creatine phosphokinase) that's being accounted for. CP is a chemical stored within the muscles that helps with the breakdown of another chemical - ATP. ATP is a chemical in your body that is broken down to produce energy. Think of it as firewood floating around in your body. As soon as you need it to, it'll burst into flames to get you going. Together, you have ATP-CP, a source of energy your body uses for about the first 45 seconds of an exercise. After this, the CP stores are depleted.
Because weightlifting requires explosive movements for about 45 second, you deplete your CP stores. According to research, these then take about 3-5 minutes for almost total resynthesis. Following the replenishing of CP, you can once again perform explosive (but short) heavy lifts.
Why compound lifts?
You're moving heavy weight. Your body can't do this for extended periods of time. Therefore working as many of your muscles as possible using the fewest number of lifts results in the greatest overall gains.
When you focus on how your body looks, you are a bodybuilder. You're not concerned with being strong, you're concerned with looking fantastic. Mr. Olympia is an extreme example of this.
But why the higher number of sets and reps with moderate weight? What about the shorter rest period?
Your goal here is to grow muscle fast. This happens through high set numbers combined with short rest periods. While information is still limited, we do know that when the CP from the ATP-CP is kept from fully regenerating, there is a buildup of lactate - a form of lactic acid. This accumulation then results in faster muscle growth. However, this muscle growth does reach its peak much more quickly.
Why the isolated lifts?
This is simply to give bodybuilders more control over shaping their bodies. Just imagine how frustrating it would be in a character creation screen if each time you adjusted your hero's arms, their chest changed as well.
Co-host of HeroesForge, founder of Battle to Be Better, gamer, singer and all around happy person.