This misses the point in that it is a function of your ambition and vision for the company. Page, or any CEO with significant control of a large, highly profitable company, could delegate any aspect of operations which fall below the level of governance by the board of directors. Or all of that except the biggest strategic projects.

But with time then freed up, the question becomes how you spend it. Do you vacation? Do you start a side project, or a bevy of them? Or, do you invest your time and energy into your highest point of leverage: your existing large, profitable company.

In the latter case, you still want ultimately to be CEO. Your goal then is to structure the company, if possible, so that it continues to fulfill its mission and to grow while you focus on the things that you feel are most important and which are most well-suited to your interests and perceived talents. For some company+CEO pairs, that may in fact be the core operations themselves. For others, it may be building toward conglomeration or investing in strategic R&D.

This helps explain the Alphabet restructuring. But it doesn't mean that suddenly Page has less to worry about. He could if he chose to step back, but as long as he feels drive to make an impact, to make the highest use of his talents, and that he can do that largely through Google/Alphabet, he'll want to remain CEO, he'll want to work hard at the company, and he'll still feel the (admittedly self-induced, chosen) pressure.

Let's also quickly look at each of the aforementioned areas of focus for a CEO who continues to have drive and believes that drive is best leveraged at their existing large, profitable company.

For some company+CEO pairs, that may in fact be the core operations themselves.

Apple is a good example here. Tim Cook could delegate whatever aspects of Apple's operation that he likes. But if he continues to have drive and views Apple as a great way to realize that drive, then his best use today is in focusing on Apple's core operations. This is because Apple's continued growth and profitability is, today, almost entirely dependent on continuing to frequently ship cutting-edge devices worldwide. That requires a very heavyweight operation, and there isn't much "revenue momentum". Apple gains network effects in the power of its brand, its distribution, and its manufacturing chain. But its revenue growth and profitability are dependent, today, on each new generation of devices. Thus, Cook had best focus there, while trying simultaneously to build toward greater "revenue momentum" in the future.

Compare this to Google, who just like Apple is also primarily dependent on one profit stream. But Google's profit stream in advertising has more self-sustaining revenue momentum. This allows Google to have focused on other areas outside the core profit operation earlier, and helps explains the Alphabet restructuring. Apple may get there one day (and it seems to me they are trying to... witness all of their recent attention on and talk about services/subscriptions), but they're not there yet. In addition, Cook is an admittedly operations focused executive, while Page is more inclined toward R&D and long-term strategy.

In combination, these things help explain how both Cook and Page can delegate as much as possible, but still remain very busy (and in very different ways) at both of their companies.

The push toward conglomeracy that Google is undergoing now is largely based on build-outs of internal brands ad operations through R&D. Others, like Disney and GE, went down the conglomeration path through combinations of internal buildouts and acquisitions. While building a conglomerate, the CEO is wisest to delegate on the core profitable operations and focus on the conglomeration process itself. This is what we're seeing with Google now, and something we may see in the future with Apple. After achieving a large and diversified conglomeration, the CEO is wisest to focus on governance/guidance/measurement and strategic guidance of the groups as a whole. This is what we've seen with GE, Disney, et al in the past.