Why the inward engines-placement on the An-124?
In general, designers would like the engines to be closer to the fuselage, more like the An-124. With the low wing on the 747, the engines have to be placed far enough out that they can still have enough clearance from the ground. This trades with the height of the landing gear and dihedral of the wing at the fuselage. With a high wing on the An-124 they have plenty of room and can place them closer.

Although the engines do provide some relief to the regular bending loads from lift on the wings, there are lots of reasons to keep the engines closer to the fuselage. Better handling with engines failed is one. But it also affects the amount of wiring and tubing you need to get to the engines, and there are other loads like hard landings that are easier to design for with the engines closer to the fuselage.