In "The Son", Siddhartha tries to win over his son: Siddhartha Jr. He does this kindly and generously, without striking or chastising his son. Siddhartha recognizes that Siddhartha Jr. has been spoiled by his mother. I have never raised an already-spoiled child, but I believe it must have felt like raising a puppy.
Recently, my dad bought my siblings and I a Bernese Mountain Dog puppy. She (our puppy is a female) is already nearly 6 months old. I try to get emotionally close to her but sometimes I end up scaring her. This just increases the emotional gap between us. On the other hand, Cumbia, our she-dog, loves my dad. Nonetheless, it is my dad the one who most chastises her. He is the one who strikes her when she pees or poos where she shouldn't, but she still loves him the most. Siddhartha tried to get close to his son by being nice and gentle with him, but by not punishing him for bad deeds, Siddhartha Jr. ended up farther away.
Although my puppy hasn't (and hopefully won't) ran away, she was forced to come into our home. She was taken out of her home. She was forced to abandon the green grasses, the open spaces, her siblings, and all her other dog friends. Likewise, in Siddhartha, Siddhartha Jr. runs away because he was taken to the hut out of necessity and not out of desire.