Stephen Hemsley hasn’t been CEO at UnitedHealth Group in nearly a decade yet he’s never really left. Hemsley, 72, has remained chairman and a major shareholder in the health care behemoth — and now is back in the CEO suite and is expected to reinstate his brand of operational and financial discipline that turbocharged the company’s growth.

We don't need to dwell on the lack of detail behind Andrew Witty stepping down as CEO of UnitedHealth ( UNH) for "personal reasons." There are plenty of public reasons to change course at a business that has become a political lightning rod and Wall Street letdown.

Stephen Hemsley ran UnitedHealth Group for more than a decade. It's a different company after four years with Andrew Witty in charge.

UnitedHealth's stock has plunged nearly 40% year-to-date as the company has battled a series of crises. Can the healthcare giant turn it around? Seeking Alpha analysts weigh in.

UnitedHealth has faced several headwinds in the recent past, ranging from a cyberattack, which had greater than initially realized impacts, to the tragic killing of its CEO, which caused the company to suffer harsh public backlash over the company's and industry practices.

Even UnitedHealth will struggle to overcome parasitic medical costs that Warren Buffett once called a tapeworm eating away at U.S. economic competitiveness. The $300 billion healthcare conglomerate reinstalled Chairman Stephen Hemsley as CEO and yanked its financial guidance.

UnitedHealth Group Inc UNH announced Tuesday morning that its CEO, Andrew Witty, will resign for personal reasons.. Stephen Hemsley, who previously held the CEO title from 2006 to 2017, will succeed him. Hemsley will also remain chairman of UnitedHealth's board of directors, and Witty will become senior adviser to the CEO.

British boss of US healthcare giant UnitedHealth quits for ‘personal reasons’ - The move comes five months after one of the company’s top executives was killed after being shot as he walked to an investor conference in New York.