Not so long ago, everyday existence was a rather risky proposition. Average life expectancy was markedly lower and you could die from an infection, eaten by some wild animal, starvation, etc, etc. The point is, everyday existence was hard and risky.
Although modern life is far from risk free, and perhaps one could argue that some risks have simply been transformed into other risks, everyday life is - in general - not as risky as what it was even a few thousand years ago.
Let's look at Jeff's life. He is filthy rich. His life doesn't feel "risky". Not only can he afford to buy food for dinner for the next billion years, but he can own farms to grow his own food and have Michelin starred chefs prepare it for him! He can afford the best house(s), car(s), airplanes, bodyguards, etc, etc. You get the picture. And he could do all this even if he got out of the "Amazon game" tomorrow.
The dude has everything, except some plain old normal everyday risk.
Even if the guy is not a super risk seeker, he probably had punani thrust before his face daily. So he engages in some risky behaviour that makes him feel alive. In fact, I'm surprised there are no stories of the guy banging supermodels.
The problem however is that first and foremost it leads to a broken family - although this happens - and secondly the billions per shag ratio is too high! This will cost him in the divorce.
As to why this woman? Who knows. Either chance, or she does it for him. Pretty or ugly is in the eye of the beerholder.