The investment manager who joined Berkshire Hathaway in 2010 was Todd Combs.
Berkshire announced Combs's hiring in October 2010. He came from Castle Point Capital, the hedge fund he founded and managed, and was recruited to oversee a significant portion of Berkshire's investment portfolio. His appointment added another specialist to Warren Buffett's investment team.
Combs later became chief executive officer of GEICO, Berkshire's major auto-insurance subsidiary, beginning in 2020. That operational role sometimes causes quiz-takers to remember him primarily as an insurance executive rather than as the investment manager who joined Berkshire in 2010.
Ted Weschler is the closest common mix-up: he joined Berkshire later, in 2011, as another investment manager. David Sokol and Lou Simpson also had important Berkshire investment and operating associations, but neither is the person described by this question.