cos(90) = 0
Sin (90) = 1
So above explanation is wrong in that respect.
T = FRsin(theta)
T = FL
FRsin(theta) = FL
RSin(Theta) = L
When will we have greatest L?
R is distance between force and point of rotation.
Theta is angle between force and position vectors.
Mathematically, Rsin(90) = L. We have biggest L when the weight is furthest from our body along the x-axis