There is no way this is evolving.
there are many animals with limbs of drastically different lengths, none of them do this. With an alternating gait like that shown, limbs have to swing through the space occupied by other limbs during movement, if the limbs that cross paths are not all swinging at the same interval they collide and your animals falls, the ground is not uniform limbs end up displaced or slightly out of sync so a certain a amount of slop (space) has to be built into the gait.
Animals with limbs of different lengths move in one of two ways. First they swing the limbs alternatively (as drawn) and just move the longer one through a shorter arc keeping all limbs in sync.
Alternatively they swing the limbs in pairs (gallop or loping) and flex the spine back to increase the arc of the hind legs. That way they swing both hing legs forward at once thus increasing the distance they move. This allows for moving at more than one speed, but it is also way more efficient. Even gorilla who's hind limbs are half the length of the front limbs move this way. if the limbs can swing between one another, this is what they will use, but then the limbs have to swing as pairs (both hind limbs together, and both front limbs together) or both hind legs can collide with each other. The only way to get around this would be to make your creature ridiculously wide, almost wider than it is long.
Look at hyena, gorilla, rabbits,or hadrosaur locomotion, to see how animals with different limb lengths move.
Also here is a great video of someone reconstructing a gorilla run cycle