Typically there's an entourage that includes the people who actually run things and/or communicate the decisions made by the oligarch. They will own the company but rarely make direct decisions for the company. They may make business decisions in the beginning of the company history but by a certain size they are detached from most operations and hand down proactive choices about what the company should be doing with its resources.

The primary vehicle for their money is the control of the company they own, the actual stocks that they borrow against for spending money.

Since they have access to any amount of money they want, there is no need to do any actual work. Any interaction with the company is just personal preference and the owner is more useful as a mouthpiece and investment magnet for the company. With few obligations each week, days start to not matter and sleep schedules are fucked. Sobriety becomes a burden since there is nothing to live for - it has all been accomplished. The only thing left to do is get drunk/high and spend money.

Owning a successful company, even a successful local business, is usually enough to detach a person from the average experience of daily work and set schedules. Millionaire business owners are just as warped as a billionaire so it becomes a question of where the shit happened. Billionaires go overseas to do fucked shit.

Anecdotally, most millionaires don't work. Some have hobbies that make a few thousand here and there but they don't worry about schedules. They are on rich time.

Edit: the ones who are in business leadership and making millions each pay period are literally sociopaths. They run shit to exercise power. They don't actually need to be there either except for some decision making meetings and coordinating with other organizations.