IIUC, the salient points are: - target area was very small (500m x 500m) for CY2. With CY3 they've made it bigger at 4km x 4km, allows for larger margin of error.

- CY2 lander had limited leeway in fixing issues, by design. CY3 has more and has landed itself, no assistance from base.

- CY2 lander had limited time to fix itself, apparently it was just a few seconds short of making it fine