It's not as if the Fed didn't know at all. They just severely underestimated the market's misunderstanding/misstepping no matter how careful the Fed might be:
Participants discussed how best to communicate the Committee's approach to decisions about its asset purchase program and how to reduce uncertainty about how the Committee might adjust its purchases in response to economic developments. Importantly, participants wanted to emphasize that the pace, composition, and extent of asset purchases would continue to be dependent on the Committee's assessment of the implications of incoming information for the economic outlook, as well as the cumulative progress toward the Committee's economic objectives since the institution of the program last September. The discussion centered on the possibility of providing a rough description of the path for asset purchases that the Committee would anticipate implementing if economic conditions evolved in a manner broadly consistent with the outcomes the Committee saw as most likely. Several participants pointed to the challenge of making it clear that policymakers necessarily weigh a broad range of economic variables and longer-run economic trends in assessing the outlook. As an alternative, some suggested providing forward guidance about asset purchases based on numerical values for one or more economic variables, broadly akin to the Committee's guidance regarding its target for the federal funds rate, arguing that such guidance would be more effective in reducing uncertainty and communicating the conditionality of policy. However, participants also noted possible disadvantages of such an approach, including that such forward guidance might inappropriately constrain the Committee's decisionmaking, or that it might prove difficult to communicate to investors and the general public.
Since the September meeting, some participants had become more confident of sustained improvement in the outlook for the labor market and so thought that a downward adjustment in asset purchases had or would likely soon become appropriate; they saw a need to clearly communicate an intention to lower the pace of purchases before long. However, to some other participants, this approach appeared likely to limit the Committee's flexibility in adjusting asset purchases in response to changes in economic conditions, which they viewed as a key element in the design of the purchase program. Others were concerned that stating an intention to slow the pace of asset purchases, even if the intention were conditional on the economy developing about in line with the Committee's expectations, might be misinterpreted as signaling an end to the addition of policy accommodation or even be seen as the initial step toward exit from the Committee's highly accommodative policy stance. It was suggested that any statement about asset purchases make clear that decisions concerning the pace of purchases are distinct from decisions concerning the federal funds rate.