What changed? The Delta variant arose and started spreading more effectively.

This is why getting spread under control is so important: each time the virus replicates there’s a chance of a new advantageous mutation making the problem harder. Wearing masks and vaccination are how we break that cycle.

The difference is that Fauci's words here are based on the available science and medical understanding at the time, and that changes rapidly as more studies are done and we are able to observe how new virus variants behave in the wild.

The vaccine hesitant's tendency to move the goalposts when their reason du jour for refusing vaccination is invalidated is based on misinformation and unfounded fear. The exact opposite of good reasons to change your mind about something.

Health leaders and politicians entire job is to build and maintain trust. Mistakes like this only reinforce vaccine hesitancy. Those that are hesitant know that the science is settled - until it isn't. The only method to account for unknown unknowns is time.

It would have been entirely possible for Fauci et. al to say "The vaccine data appears to show 95%+ efficacy, but we will be waiting to lift lockdown mandates be sure". That kind of messaging shows both a respect for science and a commitment to everyone's health. However, it was an unpopular political decision, so mandates were lifted.

This isn't the first time they've changed their course after making a decision prematurely. To the vaccine hesitant, why is this FDA approval any different? There's massive political pressure to approve these vaccines.

Plenty of people said on day 1 that this was very similar to the 1918 pandemic, which resulted in the "seasonal flu". It wouldn't be crazy for the same thing to happen here.