Why is Tathagata so cruel to the Monkey King?

In fact, I don't think Tathagata is cruel to the Monkey King, but I expect him to correct his way and stop being stubborn.

Whether in books or TV series, Tathagata's attitude towards the Monkey King is like a kind father to a stubborn son, but he is a very sensible father. I think it's a pity that the Monkey King is too spiritual and stubborn. He wanted to transform the Monkey King and give the Monkey King a chance to turn over a new leaf, but he didn't cherish it, so Tathagata could only keep him at the foot of the mountain for 500 years.

And people like Tathagata who have long been indifferent to life and death, I think he should have suffered a lot, and he also knows that suffering is the best way to hone people, so in order to turn over a new leaf as soon as possible, the Monkey King was a little stricter with him.

However, he also gave the Monkey King a chance. Five hundred years later, when the Tathagata sat down, his disciple Jin saved the Monkey King. Although Guanyin told the Monkey King, it was a revelation from the Buddha.