More than two months after Pacific Investment Management Co.’s former Chief Executive Officer Mohamed El-Erian announced his resignation from the world’s biggest bond manager, Bill Gross is still looking for a reason.

Gross, 69, speaking in an interview with Bloomberg Television’s Trish Regan yesterday, said El-Erian’s departure is still a mystery for him and a disappointment for the Newport Beach, California-based firm, which manages the industry’s biggest bond fund. He said he may have been premature in anointing El-Erian as his sole successor.

“He simply said he was not the man to take the company forward,” Gross, who manages the $232 billion Total Return Fund, said in the interview. “I would say, ‘Come on, Mohamed, tell us why’.”

The co-founder of Pimco is challenging El-Erian to speak up as he seeks to counter media reports that have painted a picture of Gross as an autocratic boss. El-Erian, who was also co-chief investment officer along with Gross, said Jan. 21 he would leave Pimco in mid-March, and his departure was followed by reports of tension between the two men. Gross lashed out at El-Erian, 55, in a June meeting as performance at his biggest fund stumbled and withdrawals continued, two people familiar with the matter said this year.

Reports of Gross as a dictator have come from former Pimco employees who have an ax to grind, the fund manager said. While he hasn’t been as inclusive and open to discussion as he could have been, he’s said he’s done things correctly to get assets at Pimco to about $2 trillion.

Performance Stumbles

“El-Erian is gone and he’s not coming back and why he left or what you might have said or done doesn’t matter,” said Erik Gordon, a professor at the Ross School of Business at the University of Michigan in Ann Arbor. “It’s time for Bill to focus on what he does for a living, which is manage bond portfolios.”

Gross, who has among the best track records over the long term, has stumbled in the past year after misreading the actions of the Federal Reserve and the direction of interest rates. Pimco Total Return declined 1.3 percent in the past year, trailing 89 percent of similarly managed funds, according to data compiled by Bloomberg. The fund suffered its 11th straight month of withdrawals in March, with clients pulling $3.1 billion, even as industrywide investors returned to bond funds.

In an internal memo to employees in January, El-Erian said he was looking forward to something different and had no plans as of then. He plans to write a book about the rise and fall of central banks, a person familiar with the matter said on March 31. El-Erian declined to comment.

Role Model