Not really sad. They are getting older, worked for themselves doing presumably what they wanted their entire career, now they are done. They could have built the company up, instead it has been common knowledge for close to 10 years they were going to retire 'any day now.'
Building a company is so fraught with pitfalls, probably realized at some point that their income was good enough that they could safely work towards retiring at some point in the future without problems and drama.
Don't be sad for them. AFAIK those that didn't retire are now at Nvidia - hopefully continuing to improve the frontend...