My grampa's friend did that and now literally has more many than he knows what to do with

This is evidence that your friend's grandpa screwed up. Indeed, after 20 years on a decent salary and retirement at half pay thereafter, I would imagine that income has long since reached the point of diminishing marginal returns, specially for someone so unconcerned with status as to live on a trailer and with no intention of giving to charity. To spend the next 20 years continuing to earn even more paychecks and a second retirement pension rather than living an eudamonic life with the little youth one has left seems like a horrible case of work for work’s sake.