what did Jackie Kennedy invest in?

https://www.nytimes.com/1994/06/02/us/onassis-leaves-estate-to-charity-and-her-children.html

Mr. Tempelsman had handled Mrs. Onassis' finances since the death of her second husband, Aristotle Onassis, and is thought to have at least quadrupled the $26 million she secured from his estate. 

The dates from the death of her second husband to her own death are March 1975 to May 1994. If she invested in the S&P 500, the total return (with dividiends reinvested) would have been 1060%, about 11X, instead Mr. Tempelsman only 4X her money.

If he invested in 3 month treasury bills, his total return would have been 3.9X her money. So he barely beat treasury bills.

So how did Jackie Kennedy work with a Belgian-American businessman, diamond magnate to manage her money and barely outperform treasury bills?