After 15 years as CEO, Tim Cook this week stepped aside, replaced with longtime executive John Ternus.

John Ternus is just the third Apple CEO in 30 years. His primary challenge is to correct the company's faltering AI strategy to preserve its position as a big tech leader.

Tim Cook will step down as Apple CEO on September 1 after 15 years, handing over the role to hardware chief John Ternus, while becoming executive chairman. Under Cook, Apples…