A decade ago, when ExxonMobil Chief Executive Officer Lee Raymond was nearing retirement and looking for a successor, Rex Tillerson seemed the perfect candidate. A 53-year-old native Texan with an engineering degree and a commanding physical presence, Tillerson was an Exxon lifer who’d spent 30 years in the “upstream” side of the business, dedicated to finding and producing oil and gas. His résumé included stints in Yemen and Thailand. Tillerson’s chief rival for the job, Ed Galante, came from the “downstream” side—refining crude and natural gas into fuels and chemicals—important but not as much as the upstream division, which accounts for about 80 percent of Exxon’s profits. In January 2006, Tillerson became chairman and CEO. By the end of the month, Galante had retired. America’s largest oil company is again looking for its next leader. Tillerson won’t hit Exxon’s mandatory retirement age of 65 until March […]