Another reason for the 1 & 3, 2 & 4 configuration instead of 1 & 4, 2 & 3, might be because that way, all the pipes, brackets, wiring looms etc can be identical on each side of each leg, so you only need one set of components rather than mirror pairs. This helps keep the spares count down.
Since, say, the right hand wheel on each leg performs one function, then if it was a left main leg, that wheel would be inboard (#2), but if it was a right leg it would be outboard, (#4), which by happy chance would give some diversity of the runway conditions too, and possible reduction of stresses as RVF750 suggests.
If you were designing an aircraft from the wheels up, with modern electronics and technology, then you would apply all the protections available to every wheel brake. This might be why aircraft such as the A330 stop on a sixpence.