In normal times, there are few words that C.E.O.s like more than “certainty.” Certainty allows executives to issue sales forecasts with oracle-like conviction. Certainty instills leaders with the confidence they need to invest $500 million in a new factory, or spend $20 billion buying a competitor. Certainty gives them the verve they need to preside over virtual town hall meetings with their employees and discuss race relations, furloughs, remote work and more.

       But at companies large and small, new and old, public and private, 2021 was a year that played havoc with expectations. Through it all, C.E.O.s swapped some of their favorite tropes — timelines, confidence, strategic plans — for something new: saying “I don’t know.” Or even: “I changed my mind.”

       Take Daily Harvest, the food delivery service. It had a major advertising campaign ready to begin this week. In the works for months, it would highlight the problems with the global food system and invite customers into the woes of modern farming. Then, days before Christmas, Rachel Drori, the chief executive, considered scrapping the campaign.

       “A week ago it felt right,” she said. With Omicron cases surging, the stock markets tanking and a pall cast over the holiday season, “it’s definitely not the right moment,” she said a few days before Christmas.

       The Daily Harvest team began a frenzied attempt to create a new set of advertisements that spoke to the nation’s unease while also encouraging potential customers to buy premade mulberry oat bowls and turmeric soup.

       Then Drori reconsidered. The original campaign would continue, after all.

       The myriad related crises of the second year of the pandemic—including a supply chain gone haywire, a topsy-turvy market and constantly evolving public health guidelines — turned executives’ projections into estimations and return-to-office dates into fairy tales.

       Companies that had prized their in-person collaborations went remote forever, with the share of Americans fully working from home rising 27 percentage points from prepandemic levels, and others remade their business models to try to stay afloat. Those decisions demanded agility: In one IBM study, 60% of executives surveyed had changed their approach to management during the crisis.

       “I’ve been in retail for 30 years now, and this absolutely feels like a uniquely disruptive time in modern business history,” said Kelly Caruso, the chief executive of Shipt, a same-day delivery service owned by Target and based in Birmingham, Ala.