A commitment that consumes the old life as fuel cannot be walked back, because there is nothing to walk back to.
An act that destroys and builds in the same motion is worth more than two separate acts, because the way back disappears at the exact moment the commitment is made. Cutting the grove and burning it under the offering to Yahweh leaves no later version of this man who can quietly return to what his father's household had always done.
Putting the altar on the height guarantees the town sees the ashes by morning, and a change other people have witnessed cannot be revised in private. Anyone who changes quietly and keeps the old materials stacked in the yard rebuilds the old thing inside a year.