ON A chilly October day in Paris in 2010, Bertrand Puech got an unexpected call on his cellphone from Bernard Arnault, the founder of luxury giant LVMH Moet Hennessy Louis Vuitton and one of the world’s richest men. Arnault told Puech, the family patriarch at rival Hermes, that his company had amassed shares in the maker of the iconic Kelly and Birkin bags. The investment was friendly and aimed at offering Hermes strategic and operational help, Arnault would later say.
