He had early detection of the situation, but refused the cut it out surgery, early on. He did all these esoteric, strange herb and natural compounds that didn't work. There was no indication that they were working, but he kept it up. He finally agreed to surgery, but everyone including him knew it was too late.
He's one of the greatest icons in the last 100 years. He had that legacy and maybe he wanted to preserve that. If Apple some how failed, that would be his legacy. He wanted to be a significant person in history as greatness.