Mr. Pilati also said that after long discussions with Mr. Zegna, “We have reached the conclusion that the mission he entrusted me with has been fulfilled” and he was ready to move on to “other projects I had put aside in order to achieve our common goals with Zegna Couture.”

In other words: It was a project, and they finished it. And there is no question that Mr. Pilati, who made his name as creative director at Yves Saint Laurent, transformed Zegna into appointment fashion-week viewing. But it seems to me three years is far too short a time to really reboot a brand’s image and solidify a new direction in consumers’ minds and closets, even in the slow-moving, detail-oriented world of men’s wear. Three years (effectively six collections) is more like a palate cleanser: a washing out of the old, and readying for the new.

It is a truism in fashion that you are only as good as your last collection, which would suggest a new designer could come in and make a statement powerful enough for it to be all that matters (see: Phoebe Philo’s debut at Céline; Tom Ford’s at Gucci). But to really add up something, you need a body of last collections. And a three-year stint simply does not allow for that.

Last month, The New York Times men’s wear critic, Guy Trebay, wrote of what would turn out to be Mr. Pilati’s final Zegna collection: “Mr. Pilati drew an imaginary line with the collection between his wealthy potential consumer and vulgar Instagram hoi polloi. His clothes conveyed the quiet aura of money, chastely created and largely invisible.”

Will that be his legacy to the brand? Or will it just be a vague memory, as a new designer comes in to impose his or her vision, leading to a head-scratching moment for consumers to wonder if they are in the same house today as they were yesterday, and where, exactly, their loyalties lie?