Yeah, you retire straight to dice
But seriously, if you have been doing something through your entire life (let's call it your true calling) and got quite good at it (money being only your secondary priority), how do you expect to quit and switch to something totally different? As I see it, it is next to impossible in practical terms. Maybe he should have started teaching poker, written a book or something. But then again, it might not be his cup of tea at all
Yes, that would be a good option for him, imo. Although I personally think that it's impossible to teach poker, because this game is evolving all the time, and a strategy that could be good 5 years ago is no longer a good one today. But forget about what I think, people are always willing to learn from the best, and since Archie Karas was the best at the time, he would never be short of students. And regarding writing a book, even if it wasn't exactly "his cup of tea", a man who turned $50 into $40 million, could definitely produce a bestseller in co-operation with a good writer.
But he thought that gods of luck were favoring him, and that's why he turned to purely luck based games like dice and baccarat, to be winning even more and faster... And that's how he lost it all.