Thomas Siebel, Technologist and Businessman, $3 billion

Tech has taken the world by storm, and some of the wealthiest people in the world today are in the same line of business. The same goes for the billionaire businessman and technologist Thomas Siebel, who made his massive fortune by being the CEO of an artificial intelligence software platform called C3.ai.

In 2004, Siebel faced some issues with poor returns from sales. All this led to him losing the leadership position in his company, passing the title of CEO to someone else, and taking the role of chairman instead.