Front axle

My son's 97 ford escort sport drivers side front axle has a lot of play. I can move the shaft at at least an inch between the inner and outer CV's.
I found it because the car was vibrating and making a lot of noise.

He just bought the car and it looks like the axle has been replaced.
What could fail in order for this to occur?

Would the CV joints fail in this manner to cause this amount of play?

The CV joints can fail in a number of ways including this one. I would check the front wheel bearing though. A lot of play in the bearing can cause this kind of movement or it is possible that whoever replaced the shaft did not properly torque the axle nut.

I'll check out the bearing when I get it apart. There is no play in the wheel so I think the bearing is probably OK