He did state it within the article.

However, directly to the point:

When they fail, it's almost always the taxpayers who bail them out. Often at immense cost. The more the risk, the higher the payoff if it works, but also the greater the damage when it don't.

By paying higher tax at the margins, there is more in the pot for when things go south. This creates a floor, rather than a ceiling, and allows for more risk with less downside in the longer term.