Mr. Iwata's health first became a known issue when he couldn't travel to last year's E3. Despite this, he persisted in running Nintendo's day-to-day operations, including standing for reelection as CEO as recently as this month. Mr. Iwata was not a poor man; he - like much of Nintendo's C-Suite - made good money during the boom times. He could have retired to focus on his health, but he decided to continue running Nintendo. It's unclear if this turn was sudden, his standing for reelection as CEO indicates that it probably was, but his health issues were undoubtedly less so.
I've had harsh judgement of some of his decisions over the years, however I've never doubted his love of the industry and the joy he found in making people happy. His dedication, right up until the end, is inspirational.