A good place to look is professional athletes where careers are very short on average and the amount of money they earn seems absurd. I think in football I heard something like average pro career being 6 months. It's no wonder the contracts are frontloaded/bonus based. In a sport like hockey where salary is guaranteed no matter what, you don't see the same bonus but frontloading occurs on really long contracts to circumvent salary caps. Back to CEOs, it just looks like rational behavior given average job length and amount of money needed to maintain a lifestyle.