Bernard Osta, Vestiaire Collective’s new C.E.O., is not your typical fashion person. A former banker, he joined the online luxury reseller as its chief strategy officer in 2021, when the Paris-based company was valued at $1 billion. Last October, after years in which the company was getting clobbered by Brexit and The RealReal, Osta took over the top job from Max Bittner, also a former banker. He had some cleanup on his to-do list. Bittner, who personally invested in the company and oversaw an acquisition of Tradesy to expand Vestiaire’s presence in the U.S., had pursued a misguided growth strategy focused on investing in technology over more salient opportunities. As a result, Vestiaire became a rare underperformer in an otherwise rocking global resale market. (A spokesperson for Vestiaire disputed the characterization of Bittner, describing him as critical to guiding the company toward profitability and delivering “significant growth.”)