I can see the local and state pols viewpoint. There was a total absence of foresight and leadership from the people who had previously taken up the task of national pandemic preparation. Also, realization of a) the leadership vacuum and b) the obligation of local governments to step up had not set in. No Cuomo, for instance. Also, no Bel Edwards who ironically has become more proactive now (better late than never) than many state governors.
On the other hand, yes, people knew what was happening. MedCram and John Campbell were putting out videos in January.. It's kind of like 9/11 where some people knew there were bad guys in the country with plans of some sort, but no one acted.
Thank god for the NBA and NCAA! Without Rudy Gobert and March Madness we'd be even worse off. Along with Washington state, they supplied needed political credibility. (H.E.B., a Texas grocery store chain, was busy preparing since January, but who did they share their info with? Probably thought of it as a competitive advantage.)
It all leaves the Mardi Gras organizers kind of off the hook of having to explain why they did nothing. As far as I know no one with enough credibility came directly to them telling them to stop though we know, I think, how they would have reacted. Party on!