The two major causes of this slowdown have been the extent of the economic effects of the Delta surge and the extent of supply constraints, both of which had larger effects than I and most forecasters expected. That was due to both the disappointingly low levels of vaccination in some areas and how highly contagious Delta proved to be.
Meanwhile, we have seen labor shortages in many regions and many sectors that seem unwarranted given the level of unemployment and other indicators of slack in the labor market. And supply constraints have been very widespread, with many causes, only some of them directly related to COVID-19.