Algodoo

Torque = Inertia x Alpha

Torque = Force x Radius
Mass of block is equal for both pulleys, so force applied downwards is equal, however since the radius on the left is 2x it has twice the torque (2T)

Inertia = (1/2) x (Mass) x (Radius)^2
Mass of the left pulley is 4M and radius is 2M, so moment of inertia is 16x greater (16I)

Since: Torque = Inertia x Alpha, and torque is 2T & Inertia is 16I, the alpha of the left pulley must be (1/8)a relative to the right pulley. Since the left pulley has twice the radius, the linear acceleration of the block should be (1/4) of the acceleration of the right block.

*However, the demonstration shows otherwise and does not seem to follow laws of inertia*