Well, because usually the heavier your capable of lifting, the larger those muscles are. IF you wanna be big like say Kazmeir or Coleman, you've got to lift some heavier than you're capable of weights, often. Hope that helps.
no it doesnt help.
what about time under load etc. what is heavier a fast not entire rom movement with much weight ,ot more reps of perfect form and slow full squeeze with moderate weight?what do you think will build more muscle?
"strenght" has to do with bone structure, cns muscle mind connection(how comes everybody has a stronger and weaker side>),and joint-tendon strenght.
cutler trains deadlifts with 3 plates a side, go tell him about your theory ahaha.
and you ignored stuff like pre exhaustion etc.
and what frozzor said, comes down to genetics period.
i hope THIS helps.